Strikeout Rate Stabilization and Time

Thanks to the wonderful work of Baseball Prospectus, we understand that strikeout rate - and other offensive categories - stabilize at a relatively small number of plate attempts. While statistic stabilization is commonly referenced, it's worth exploring what this means - and how it can be taken advantage of.

Rate stabilization gives us a sense of how small of a sample size is needed before a player's average talent can be estimated. Baseball Prospectus determines this by finding the sample size at which any randomly selected sample has a high correlation (over 0.70, to be exact) with any other randomly selected sample of the same size. For example, Manny Machado's last 60 plate attempts should feature a strikeout rate that is highly correlated with his strikeout rate over 60 plate attempts in 2015. Further, Manny Machado's strikeout rate over any 60 plate attempts, even non-continuous ones, is highly correlated with his strikeout rate over any 60 other plate attempts. The concept of course makes perfect sense: a player is who he is, and has a true level of ability. The important part is the number of plate attempts it take to estimate with a degree of certainty a player's true talent level.

The concept of rate stabilization is frequently used to make judgments on a player's ability early in the season, or sometimes early in his career - and they should be. The concept of rate stabilization is proven over the entire population of Major League Baseball and holds true overall. However, in the interest of testing heuristics, I sought to understand how much variation there is in a player's 60 plate attempt strikeout rate over time. The addition of time is, I think, very relevant to understanding a player's true talent level, and something that I might argue is missing from the common knowledge on any rate stabilization.

I want to bring time into the conversation of rate stabilization because it allows for players to grow, adapt to the speed of the Majors, change their approach, fix their swing,... Basically for players, especially young players, to mature into the professional ballplayer that they will be for the majority of their careers. It wouldn't be fair to assume Albert Pujols' 13.8% strikeout rate in his first season was his true level of talent and to be repeated for the next 17 years of his career. In fact, Pujols recorded sub-10% strikeout rates in nine of the next eleven seasons.

Was Pujols simply lucky in the first 10 years of his career to consistently record strikeout rates below that of his first year? It's far more likely that his true, natural strikeout rate decreased (read: his true talent level increased) as he grew to know the speed of MLB pitching and learned tendencies and pitch sequences and studied film and practiced. Pujols probably practiced a lot. How many other players can we identify as elevating (or lowering) their level of true talent rapidly - before seasons end or before they become a coveted free agent?

I believe we can, and I set out to do so among Orioles players. Consider this a proof of concept. By examining the rolling 60 plate attempt strikeout rate of Orioles players, we can observe instances in which a batter is striking out more or less often (a LOWESS line makes this trend easier to pick out). We expect some variation, obviously, since performance over 60 plate attempts is simply correlated with performance over 60 other plate attempts. However, a player that is consistently lowering his 60-plate-attempt strikeout rate may have actually improved his ability to not strike out (be it through better contact rates, zone awareness, or pitch recognition). In an attempt to parse out which changes are worth taking note of, I also plotted the number of standard deviations from the mean strikeout rate that the 60-plate-appearance strikeout rate falls. Sustained periods of time that are greater than 1 standard deviation are worth considering as repeatable, new normals. Doing so would require digging into data and talking with the player to understand why his strikeout rate is so different than normal, and if it's a new repeatable skill.

Take, for example, Machado. His 60-plate-attempt strikeout rate has increased over the last few hundred rolling instances of 60 continuous plate attempts. Although Manny's rolling 60-plate-attempt strikeout rate is still less than one standard deviation from his mean, we might begin to wonder whether his true strikeout rate is a bit higher than it was when he entered the league. This is not necessarily a bad thing. Although, yes, all else equal, a lower strikeout rate is better, all is rarely ever equal. Strikeouts are usually the price of hitting for more power. This is not an exercise to say that Machado should change his approach at the plate lest his value drop because of his strikeout rate, but instead to recognize that in hitting for more power, Manny's strikeouts might increase.

Consider also Mark Trumbo, whose extraordinary 2016 was his third out of the last four years to feature a strikeout rate of less than 25%. Trumbo has demonstrated a strikeout rate about a half of a standard deviation below his career average for long enough that we might begin to question whether his recent performance is a better indicator of his talent than his career average:

Ryan Flaherty's 60-plate-attempt strikeout rate has consistently increased since 2013, ranging from a full standard deviation below his career average to nearly a standard deviation above average. Perhaps it's no surprise that offensive opportunities have dried up for Flaherty:

And finally, Joey Rickard has only six plate attempts this season but rolling plate attempts over seasons shows a pretty dramatic decrease in 60-plate-attempt strikeout rate. With some practice and some exposure to Major League pitching, Rickard may have learned to handle the strike zone a little better than when he first entered the league. This is an instance where a player's improvement would merit some further investigation; Rickard has never been much for on base percentage, but slight changes in approach might have made his offense slightly more valuable than expected. Obvious follow up questions that seek to determine whether Rickard has actually gained more control of the strike zone include whether Rickard is swinging less often, swinging at pitches out of the zone less often, whiffing less often, and walking more (walk rate stabilizes over 120 plate attempts).

Rickard is also a fine example of an instance in which this method might be used to judge a young player's performance with more information than his career averages or any randomly selected 60 plate attempts. We should expect Rickard to have grown and adapted to Major League pitching; to expect his potential and performance at ages 25-30 to match identically his performance at age 24, which he was getting his very first exposure to the Majors, would be rather shortsighted. Rickard may not ever be a stud (he won't be), but he might scratch the replacement level mark this season as a batter with a 15% strikeout rate instead of the 20% strikeout rate he's projected by ZiPS and Steamer to exhibit.

A prospect with more promise or better peripherals might show a similarly snaking rolling 60-plate-attempt strikeout rate over his first season or two. This might prompt a team to focus on or reinforce plate discipline, contact, or control over the zone depending on the drivers of the change in strikeout rate. Similarly, if an established player exhibits a strikeout rate consistently below his career strikeout rate, a team might consider his career average to underestimate his ability to reduce strikeouts.

Chris Davis Should Swing More

One of the longstanding criticisms about the Orioles offense is their penchant to avoid walks like the plague. Since 2012, the Orioles rank 23rd in baseball in OBP, despite the fact that they are 6th in runs scored. The biggest reason? The team has hit far and away the most home runs in baseball during that time frame. One of the biggest reasons for that? Chris Davis, who leads all of baseball with 197 homers during that time.

Of course, Davis has been the best OBP guy on the team, posting a .340 OBP since 2012, a mark surpassed only by Nick Markakis (in fewer PA, naturally).  Even in what has to be considered a down season in 2016, Davis still finished second on the team with a .332 OBP, and in general runs an OBP that is far better than his batting average, making him almost like a unicorn on this particular team.

This should be great! The O's need OBP guys, and Davis is one of the most patient hitters on the team. It's likely one of the reasons that he may be the best leadoff option on the team.  The problem, however, is that the more selective Davis has been in his career, the less success he has seen overall. Davis' walk rate has increased every single season since 2012, with his 13.2% in 2016 representing a career high, but produced his two worst offensive seasons in 2014 and 2016. This is a puzzle, as in general we'd expect high walk rates to correlate with increased offensive success.

One of the factors that may be able to explain this somewhat odd occurrence is to look at how often Davis actually swings the bat, since you can't hit homers and produce big offensive numbers unless you hit the ball.  Davis swung at his lowest rate ever last season, swinging at just 42.7% of pitches. His career mark is 49.4%, and in his breakout 2013 season he swung at over 50% of the pitches he saw. To his credit, Davis swung at the fewest pitches outside of the strike zone in his career last season, but the flip side of that is he swung at the fewest percentage of pitches in the zone as well. In fact, the decline in this metric was so precipitous that it almost leads me to question whether his hand injury was far more severe than was reported. Unless his eyesight also declined last season, there is little other reason for why he went from swinging at 68% of strikes in 2015 to just under 60% in 2016.

This also brings up the issue of strikeouts, which is something that any discussion of Davis simply can't avoid. That Davis strikes out a lot is not news. What is interesting, however, is how he strikes out. Davis has, by far, the most called third strikes in baseball since 2012 with 279, and had 79 called third strikes in 2016, which is also the most by far for any player in any season since 2009.  Some of that is a simply function of the sheer volume of strikeouts he racks up, but looking a bit deeper into the yearly fluctuations of called K's is particularly interesting. Below is a table of Davis' called strikeout percentage, his Weighted Runs Created (WRC+) and his Weighted On Base Average (wOBA) by year.

Year	Called K%	WRC+	wOBA
2012	24	121	0.352
2013	24	168	0.421
2014	32	94	0.308
2015	27	148	0.390
2016	36	111	0.340

In years when Davis takes fewer called third strikes, he is at worst an above average hitter and at best one of the game's elites. In years where he takes a higher number of called third strikes, however, he is below average to slightly above.

Now, this may be sample size noise and there are likely other factors that contribute to Davis' offensive inconsistency, but it seems fairly clear that the less aggressive Davis is the less successful he is offensively. A strikeout is an out regardless, but a called third strike is probably the least productive out simply because there is no possibility of anything good happening. In Davis' case, it's doubly unproductive because he hits the ball extremely hard. He consistently ranks in the upper echelon of hard hit balls and obviously produces massive power when he connects.  

It seems odd to say that a player should be less selective, and even more so when that player is on the Baltimore Orioles. In Davis' case, however, taking fewer pitches and being more aggressive at the plate certainly seems to correlate with better offensive production.  So, I'd suggest something I never thought I'd have to to suggest to an Oriole: swing the bat!

You Don't Have To Like The Orioles Striking Out So Much, But You Knew It Was Going To Happen

I hope you're sitting down when you read this: The Orioles assembled a team of power hitters, and they are striking out a lot. Sometimes, they are going to have games where they impress with powerful home run displays. They've done that. Other times, they are going to frustrate and run off stretches when they're not scoring a bunch of runs and look lost at the plate. They're in the middle of one of those brutal stretches right now, and Tuesday night's 19-strikeout, extra-inning loss was a prime, tough-to-watch example. They even managed to follow that up by striking out 18 times in nine innings on Wednesday.

Apparently Tuesday's struggles frustrated some more than others. Peter Schmuck of The Baltimore Sun singled out Adam Jones's quote in this Jon Meoli story about strikeouts being "part of [the Orioles'] DNA as a team." As usual, Jones had other interesting things to say, but it's not all that surprising that someone focused on the DNA comment and wrote something negative about it.

No one likes to see his or her favorite team's hitters constantly flail away at the plate, especially in crucial situations. It's maddening. As of last night, the O's were 10th in the majors in strikeout percentage, so surely fans of the teams above them feel similarly at times just as often, if not more.

Maybe Schmuck's angle is that O's batters shouldn't accept their whiffing ways, or that saying they're going to strike out means they aren't doing anything to prevent it. Or maybe the larger point is about wanting games to be more aesthetically pleasing (more balls in play, etc.) instead of swing and miss after swing and miss. The former seems ridiculous, but perhaps the latter is a discussion worth having. I don't really share that opinion, but many do.

Anyway, unless you really think Jones's comments mean the O's aren't trying or aren't striving to get better, then nothing about what the Orioles have done at the plate should be surprising. They rank 10th in runs per game in the majors, and the goal is still to score as many runs as possible. Maybe they should even be striking out more, considering the various free-swinging sluggers in their lineup.

In a March post for FanGraphs -- titled "Are the Orioles Going to Strike Out Too Much?" because everyone knew the Orioles put together a lineup full of windmills -- Dave Cameron noted that "team strikeout rate doesn’t really have a negative impact on the number of runs a team scores relative to expectations" before moving on to an analysis of extreme strikeout teams underperforming their BaseRuns projections.

Along those lines, it's reasonable to worry about the team's level of production in clutch situations as the season goes along, because high-strikeout teams might not be as good in that department. But it is silly for Schmuck to assert that "opposing advance scouts just [discovered] how vulnerable the Orioles are to a steady diet of offspeed stuff that breaks under and around the strike zone." The O's are a collection of mostly veteran players that have been heavily scouted, so give both them, the pitchers they are facing, and advanced scouts more credit than that. You don't think teams in the American League East know several O's hitters are vulnerable to pitches out of the strike zone? If not, then they need new scouts.

The Orioles haven't looked good at the plate lately. Some of that is the result of a long season, with normal ebbs and flows. Some of that is because this is what the O's lineup will occasionally look like. And some of that is because of certain players getting more playing time than they probably should, or batting in non-optimal spots in the lineup. The O's roster has holes that Buck Showalter can't hide.

In both 2014 and 2015, the O's were in the top 10 of highest strikeout percentage teams, and they still finished with top 10 offenses. In 2013, the O's were much lower in strikeouts (23rd) but placed fifth in runs scored. None of those teams won the World Series, because the number of strikeouts isn't the sole determinant of who prevails and who doesn't.

If you want to criticize anything, then rail against how this team was put together. But considering that the O's are still eight games above .500, that would be strange timing.

Why Chris Davis Is Not A Rally-Killer

 

Photo by Keith Allison

During last week’s Camden Highball podcast, I made the following statement (paraphrased):

I love you, Chris Davis. But I don’t want you batting in the bottom of the 9th when the team is down by two and there are two runners on base. One-third of the time you’re going to strike out (not advance the runner). These little moments are going to add up during the year.

Prior to recording the podcast I’d thought a lot about the relationship between swinging strike rate and WPA. My gut told me a high-strikeout player like Davis would hurt the team by failing to advance runners in close games.

It seemed true. It felt true. So I said it out loud.

After I listened to the recording, an embarrassed flush spread to my cheeks. Here I am, writing on a sabermetrics web site, and I just used my gut to make a statement. Ugh! We all say foolish things, but not many of us get the chance to say foolish things that strangers on the Internet hear and that live for eternity on Dropbox. I managed to do both at once.

In order to feel less foolish, I had to atone for my sins. Isn't that what this whole sabermetrics thing is about, backing up your beliefs with evidence? So I said "gut, I'm sorry, but I need to fact check you." My gut responded favorably, but that's probably because I'd just eaten a peanut butter creme Oreo.

I examined the relationship between a player's swinging strike rate and the following metrics:

• Win Probability Added: Measures how much a player added to their team’s chance to win during the course of a season, taking into account both the leverages (inning, score, runners on base, number of outs) in which they batted and how well they did in the plate appearance.
• Win Probability Added / Leverage Index (WPA/LI): WPA without the leverage component. Unlike WPA, WPA/LI doesn't punish players for appearing in lots of low-leverage situations, nor does it reward players to bat in a lot of high-leverage situations. Players can't control the leverage of the situations in which they bat.

I sampled non-pitchers from 2010-2015 who averaged at least 50 PA per season. This low threshold avoided survivor bias by looking at not only starters, but also role players and those who were injured.

My hypothesis: players with high swinging-strike rates will have a lower WPA than players with low or average swinging strike rates. For context, Davis’ swinging strike rate of 15.48% ranks 20th-highest out of 1,607 players in this sample.

Unfortunately for my gut, the research shows swinging strike rate doesn't correlate well to either WPA or WPA/LI:

Swinging strike rate explains only 0.07% of the variance in WPA, or about 0.002 wins per year. That's a tiny number of wins.

The relationship isn't much stronger when you remove leverage from the equation. The r^2 between swinging strike rate explains only 0.0198 wins of WPA/LI per year. No one will notice this change in a player's WAR.

But r^2 isn't everything. The regression lines slope upward, indicating that as swinging strike rate increases, WPA and WPA/LI also increase. If you followed this model you'd want a player to swing and miss as much as possible, because the model says their WPA would be very high. But no one wants a batter to swing and miss ever, let alone "as much as possible".

That's why the plots look different if you focus on players with medium-to-high swinging strike rates:

The r^2 values remain weak. More importantly, these trend lines slope downward. Now the model says: if you swing and miss a lot, you're starting from a deeper hole than your peers who make more contact. You can still make a positive contribution, but you'll have a harder time doing so. There's the logical sense we are looking for.

A 2nd-degree polynomial fit of the original data shows this effect better:

While Chris Davis' swinging strike rate doesn't explain his WPA or WPA/LI, he should be careful going forward. If he swings and misses much more than he does now, he'll have a harder time contributing to the team.

Fortunately, Davis is a more complete player than just swinging and missing. He possesses tremendous power and mixes in a pretty good walk rate. These factors boost his wOBA, which correlates much better with WPA and WPA/LI:

The r^2 between wOBA and WPA is 0.64 (2.1 wins), and between wOBA and WPA/LI it's a whopping 0.82 (2.3 wins). Overall offensive prowess, as measured by wOBA, explains variance in WPA and WPA/LI much better than than swinging strike rate does.

These relationships hold up well for hitters in Davis' class:

In both cases, the regression models make logical sense. Have a high wOBA and you'll contribute wins to your team. Chris Davis should have a high wOBA. All is right with the universe.

I'm sorry, Chris Davis. I take back what I said. I won't grimace in frustration anymore when I see you bat in a high-leverage spot. I'll remind myself that you're a very talented baseball player who whacks the ball all over the yard, no matter the game situation.

But please don't swing and miss any more than you already do.

Adam Jones Has Better Plate Discipline Than Chris Davis

The Orioles recently re-signed Chris Davis to a seven-year, $161 million contract. As Jon wrote, Davis brings to the immediate a strong bat with a heavy right-handed favored split.  It’s pretty simple, people like Chris Davis because he has elite power and can absolutely crush pitches. Meanwhile, CBS Sports feels that he still strikes out a lot, but made small strides with his plate discipline last season.  The writer argues that Davis’s BB/K ratio of .4 may not be ideal but isn’t terrible either. People generally seem to agree that Chris Davis may strike out a lot but his walk rate does offset it to some extent.

On the other hand, it is pretty well accepted that Adam Jones has bad plate discipline. Bucs Dugout asserts that Adam Jones swings at pretty much everything. Peter Gammons claims that his major problem is that he swings too often in favorable counts. Camden Chat says that it’s indisputable that he strikes out too much and walks too little.

In this article, I intend to show that Chris Davis has significantly worse plate discipline than Adam Jones, despite the fact that Davis has a BB/K of roughly .4 while Jones has a BB/K of roughly .2 over the past three years.  Here, let me explain.

Recently, I wrote a post breaking wOBA into three component parts using data from ESPN Stats and Information. I measured a player’s production when he hits a pitch in the strike zone, when he hits a pitch that isn’t in the strike zone, and when he doesn’t make contact at all. Using this method measures each player’s production in these three areas as shown in the chart below.

Chris Davis averages a wOBA of .187 on balls not put into play compared to Adam Jones who averages a .136 on balls not put into play from 2013-2015. This makes sense as Chris Davis does walk more often than Adam Jones and would seem to support the argument that Davis has better plate discipline. However, such an analysis ignores one crucial thing. It ignores the fact that Adam Jones failed to put the ball into play 24% of the time while Chris Davis failed to do so 44% of the time.

This is relevant due to a point that I made in my previous post. For the average batter, a strikeout is more damaging than a walk is beneficial. Batters only have a .219 wOBA on average when failing to put the ball into play and nearly all do better when they put the ball into play than when they fail to do so. The general rule of thumb is that it takes roughly 11 walks to offset 9 strikeouts because batters average a .369 wOBA when putting the ball into play.

In order to compare Adam Jones’ plate discipline to Chris Davis, it is necessary to take into account the fact that Chris Davis doesn’t put the ball into play as often.  Just comparing .187 to .136 fails to take quantity into account.

The way to take into account both quality and quantity requires some high school algebra. It requires comparing how Adam Jones actually performed to how he’d perform if he put a pitch into play only in 56% of PAs and failed to do so in the other 44% but had the same wOBA when not putting the same ball into play as Chris Davis. In other words, this is equivalent of determining which equation is greater:

.76 * wOBA Jones InPlay + .24 *wOBA Jones NotInPlay  or
.56 * wOBA Jones InPlay  + .44 *wOBA CD NotInPlay.
Which simplifies to:
.2 * wOBA AJ InPlay + .24 wOBA AJ NotInPlay vs .44 * CD wOBA NotInPlay

In other words, it’s necessary to compare how Chris Davis performs during the 44% of times when he fails to put the ball into contact to how Adam Jones performs during the 24% of times he fails to put the ball into contact AND another 20% of how he performs when he does put the ball into contact. This results in the following.

When one takes both quantity and quality into account, it becomes apparent that a player able to hit the ball as successfully as Adam Jones would rather have his walk and strikeout numbers rather than having Chris Davis’s. Even though Chris Davis has a better BB/K and a wOBA Not in Play than Adam Jones, the fact that he puts so many fewer balls into play hurts him.

I make two assumptions for this analysis. I assume that Adam Jones will hit the same proportion of pitches in the strike zone or not in the strike zone if he makes contact less frequently and that his production when he does make contact won’t increase if he swings less frequently. Preliminary research suggests that these assumptions are slightly inaccurate. He should be expected to make slightly better contact if he swings less frequently.

The wOBA All Balls Field projects how Adam Jones would perform if the extra in play contact was solely against pitches out of the strike zone and thus balances out both of the assumptions in the paragraph below. Even still, one would rather have Adam Jones’ numbers than Chris Davis’s strikeout and walk numbers. In reality, as shown in the chart above, Chris Davis’s plate discipline is about as good as Jonathan Schoop’s and only slightly better than Jimmy Paredes.

This poor plate discipline shows why it’s so hard for Chris Davis to be successful.  My metric measuring plate discipline suggests that he’s typically in the bottom 2% in this regard (5th percentile in 2014). He’s able to thrive because in 2013 and 2015, he was in the 99th percentile of wOBA for pitches hit into play. He was elite in those years because he was able to kill the ball whenever he hit it. In 2014, he was in the 86th percentile in wOBA for pitches hit into play. As soon he drops from elite to very good in wOBA for pitches put into play, he becomes an average hitter.

As the chart below shows, when he’s in the 99th percentile for wOBA for pitches in play, he’s in the top five percent of all batters. If he drops to just the 95th percentile for wOBA for pitches in play, all of a sudden he’s down to the 77th percentile of all batters. If he drops to the 90th percentile, then he’s in the 65th percentile of all batters. Once he drops to the 75th percentile for wOBA for pitches in play, he’s in the 36th percentile of all batters and is a DFA candidate. The takeaway is that he can still be one of the best batters when putting pitches into play and still be worthless. The chart below shows where he ranks based on his wOBA for pitches in play.

The news gets even worse. On Twitter, Jon stated that he felt that Chris Davis had a good chance of becoming ineffective due to a collapse in offense if his contact rate drops any further because his walking ability is an indirect effect of his hard contact. I figured that was unlikely because I presumed that Davis will be average offensively before his ability to make hard contact degrades significantly. But when I looked at the data, it became clear that one could argue that Davis always had elite numbers when putting pitches into play but struggled earlier in his career because he hits few pitches in the strike zone compared to other batters and had a poor walk vs. strikeout ratio.

In addition, while Adam Dunn, Carlos Pena, and Jarrod Saltalamacchia each became ineffective once their wOBA when putting pitches into play degraded, it would appear that Melvin Upton and Ryan Howard started to become ineffective when their plate discipline degraded. It seems reasonable to presume that Chris Davis will start struggling if his primary competency of hammering pitches put into play starts to falter or if his plate discipline becomes significantly worse. It’s reasonable to argue that Jon and I both have reasonable chances of being right.

Chris Davis probably won’t become ineffective immediately, but should before his contract ends. There are a few encouraging outliers though. David Ortiz didn’t stop being elite in this regard until he was 36 while Nelson Cruz is still elite at 35. Davis’s contract only runs through 36 so if he can take after those players then the Orioles will likely be happy with the results of this signing. On the other hand, Ryan Howard started struggling at 32 and Adam Dunn started struggling at 31. This contract may look ugly if the Orioles only receive three years of strong performance from Davis.

This article shows that most players would rather have Adam Jones’ walk and strikeout percentages rather than Chris Davis. If so, this suggests that plate discipline is largely misunderstood and that a metric similar to K-BB should be used for both hitters and pitchers. With a few exceptions for players like Nori Aoki and Alberto Callaspo, it is better to put the ball into play than not. Indeed, in 2013, Chris Davis had a .657 wOBA when putting a pitch in the strike zone into play while a player that walked in every plate appearance would have a .690 wOBA.  It's easiest for batters to be successful by putting the ball into play.