06 May 2015

A Second Look at Chris Davis

A few weeks ago, I took a look at Chris Davis in which I noted that he was having trouble hitting fastballs. Since then, he has put up a .294/.381/.588 line. In 42 PAs, he has been walked 6 times and struck out 14 times (bad but definitely an improvement). For the season, his swinging strike rate has dropped from 18.6% to 15.3% and his plate discipline statistics are beginning to conform with past season norms. 

The main reason why he’s been so successful over this period is ironically due to his success hitting four-seamers. He has put 8 of the 67 that he’s faced from 4/21 to 5/3 into play and they have gone for four singles, two home runs and two outs.  Hits on four-seam fastballs account for 6 of the 10 hits he’s had over that successful period. 

It should come as no surprise that his foul and whiff rate has dropped significantly over this period and his balls in play have increased significantly. It is interesting to note that his 2015 numbers against fastballs are beginning to look similar to his 2014 numbers. This chart, using stats primarily provided by Brooks Baseball, illustrates that point.

So, what has changed? One possibility is small sample size. It is possible that looking at only 77 four-seam fastballs was simply too small of a sample to come to any conclusions and that I should have waited until Davis had faced 150 or even 200. However, I think a better understanding of what it means when a statistic has reached the point of stability can help explain why that may not necessarily be the case.

Contrary to popular belief, when a statistic reaches the point of stability, it doesn’t mean one should expect a player to continue performing the same way for the rest of the year. All it means is that the given sample size is large enough to measure what a player did during that time frame. Basically, one wouldn’t say that Chris Davis is struggling if he has a game where he strikes out every time he is at bat because even players doing well can have a bad game. But one would say that Chris Davis is struggling if he struck out in each of his plate appearances for two weeks. The point of stability helps us quantify when we should worry about a players’ results.  It’s more helpful in telling people what did happen than what will happen in the future.

This does have some use when attempting to predict the future because past performance does help us determine which players will do well in the future. It is reasonable to predict that Miguel Cabrera will hit better than Ryan Flaherty in 2015 because of Cabrera’s track record. However, we may not be so willing to presume that a player will be good based solely on one sample. After all, Brian Matusz had a strong 2010 as a starter and based on that sample looked to be a mainstay in the rotation for a number of years. Needless to say, that didn’t happen. Basically, one sample may tell us what happened during that time frame but we require multiple samples to be really certain about the results for a player.  That doesn’t mean that one sample isn’t interesting, but rather that we should be careful to put it in its proper context.

That means that it’s reasonable to presume (even if we can’t prove it) that Davis was struggling earlier in the year and there could have been a number of reasons why this was the case. It could be possible that he was simply getting used to facing major league pitching after a long suspension last year. It could be possible that he was in a legitimate slump and his manager decided that more practice would help him get out of it. It could be possible that Chris Davis was focusing on hitting other pitches for the first few weeks and decided to focus on fastballs for the past few weeks.

The interesting thing about looking at how a hitter deals with certain pitches is that it is something that a coach can address relatively easily. It’s hard to find a way to get a batter to walk more often while still maintaining the same level of power and avoiding strikeouts.  It’s considerably easier for a batting coach to have a given batter focus in practice on primarily hitting fastballs. For something like this, you would want to raise a red flag earlier than necessary in order to address a potential problem but it wouldn’t be clear that it’s an actual problem until it continued occurring for a few samples despite attempts to address it. In other words, unlike many other statistics that describe how well a player performs, these statistics can help describe why a player is performing the way he does and therefore can be relatively easily addressed.  

Over the past ten games Chris Davis has started to hit fastballs and has gone on a strong hitting streak.  If he was struggling to hit fastballs to start the season then he certainly isn’t now. I think that this might just show that Chris Davis was having problems with fastballs and found a way to fix it.

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