The Transformation of Jake Arrieta

Let's take a break from the endless assault of spring training tweets and photos and talk about Jake Arrieta. Spoiler alert: Arrieta no longer pitches for the Orioles. In the summer of 2013, he was shipped to the Chicago Cubs along with Pedro Strop and some international bonus pool money in exchange for Scott Feldman and Steve Clevenger. As Joe noted at the time, it was "a classic trade in which a contender trades long-term assets to a non-contender for a short-term asset." And Feldman was perfectly serviceable and did help the Orioles, though they still missed out on a playoff spot.

Feldman signed with the Astros after the 2013 season and Clevenger has been mediocre in limited major league duty. Strop immediately turned things around in Chicago, and he's been very good in a season and a half. But the real prize in the deal turned out to be Arrieta, who had a career year in 2014 and is under team control through 2017.

Arrieta got a late start last season because of some shoulder inflammation, but when he was finally able to go in early May, he pitched very well. Out of all pitchers who threw at least 150 innings, Arrieta was 11th in fWAR (4.9), 10th in ERA (2.53), and second in FIP (2.26). He established career bests in innings pitched, strikeout rate, walk rate, home run rate, groundball percentage, and home run/fly ball ratio (and obviously in ERA, FIP, and WAR).

Combined with the decent but not nearly as good numbers Arrieta posted in 50-plus innings in 2013 after coming over to the Cubs, here are how his numbers stack up in Baltimore vs. Chicago:

Team	IP	ERA	FIP	K/9	BB/9	bWAR	fWAR
Orioles	358	5.46	4.72	7.0	4.0	0.3	2.7
Cubs	208.1	2.81	2.92	8.8	2.8	6.0	4.8

So, yes, Arrieta has been much, much better in Chicago than in Baltimore. So what has he done differently?

Arrieta has been more effective at keeping pitches low in the strike zone. Here's his zone profile while with the Orioles:

And here's his zone breakdown with the Cubs:

And while Arrieta's strikeouts are up and walks are down, he hasn't been pounding the zone more. He actually threw fewer pitches in the strike zone in 2014 (47%) than his career average (48.7%). But he has been getting more swings and misses, especially on low pitches. Arrieta hasn't needed to throw as many pitches in the zone because opposing batters are swinging more often at pitches outside the zone and making less contact. They also swung a bit more on pitches in the zone and still made less contact.

A big part of Arrieta's success has been a pitch addition. Here's his pitch usage breakdown while with the Orioles and Cubs:

With Orioles: 30% four-seam; 31% sinker; 16% slider; 15% curve; 8% change
With Cubs: 21% four-seam; 31% sinker; 26% slider; 17% curve; 5% change

Arrieta has traded four-seamers for more sliders -- or, more accurately, more cutters -- and it's been a devastating weapon for him. He's been much better at controlling his cutter and using it more in fastball counts.

It's known that Dan Duquette and Rick Peterson (the O's director of pitching development) are not huge fans of the cutter. They prefer that their young pitchers work on other secondary pitches, and they also believe that overuse of the pitch can cause a decrease in velocity. Baseball America covered the cutter and a possible decline in velocity in 2010, and Dan Haren talked about it last year. An interesting part of Haren's interview: ". . . the cutter 'absolutely' leads to velocity loss. (He just didn’t care because he was already losing velocity.)" (Read more on the O's and the cutter here and here. The O's are more extreme when it comes to worrying about the effects of the pitch, but there isn't a great data set to entirely prove that some of their concerns aren't justified.)

Arrieta has actually seen an uptick in velocity with the Cubs. His fastball velocity jumped about 1 mph. He's throwing his cutter about 3 mph harder than his slider in Baltimore. And even his curveball has seen a 2 mph bump. Cutters tend to be late-career pitch additions, so it is interesting to see Arrieta add the pitch in his late-20s and also still see an increase in his velocity across the board. Perhaps that won't continue. But for at least one season, Arrieta pitched better than he ever did in Baltimore -- by far.

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Plenty of factors have had a part in Arrieta's flourishing with the Cubs. He's been mostly healthy, he's pitching in the National League Central instead of the American League East, and he went to a team that embraced the use of the cutter and tweaked his mechanics enough to show him how to throw it properly. Arrieta also admitted that changing teams helped:

It can’t really be as simple as the change-of-scenery theory floated almost every time [Theo] Epstein’s front office acquires a new pitcher.

“It’s so hard to know,” Arrieta said. “It’s one of those things where I was at a point where one small thing needed to happen — and that happened to be it. I feel like I was in a situation where I was pretty much standing on the edge. Just wasn’t able to get over.”

Cubs general manager Jed Hoyer also had a smart comment about change of scenery in general:

“Sometimes, I think it’s probably as much as trying to impress in a new place. Sometimes, it’s probably as much as being able to feel like your new employer likes you maybe better than your old employer did. You’re excited to be in a fresh environment. . . . Things can get stale or get negative in a place for a player and they can go somewhere else and be a different person.” 

Arrieta's challenge now will be to do something he's never done before: keep pitching well after having almost a full season of fantastic work. It would have been great if he'd been able to succeed in Baltimore, but his turnaround has been remarkable and it's a lot of fun to watch him pitch (especially for Cubs fans).