Thursday, January 9, 2014

Coors Field and Ground Already Trod

Back in November, I wrote about Coors Field. I noted that it's favorable for hitters not only because batted balls carry better there, which is kind of Physics 101, but also that pitches with movement, like curveballs, don't break as much, making them easier to hit. 

It turns out I wasn't being particularly original in my analysis. Last April, this article appeared by Dan Rozenson at Baseball Prospectus. It gets into some technical detail about how pitches move (you'll learn the term "spin deflection," among others), with the conclusion that: 
There is strong evidence that the slider performs in absolute and comparative terms better than the curveball in Coors Field . . . Sinking fastballs also have a sharp drop-off in performance at Coors, and there is some evidence that using a cut fastball would be a good alternative.
With that in mind, let's break down the Rockies' starters last year, using pitch type analysis from Brooks Baseball, with a particular eye toward slider usage:
  • Jhoulys Chacin (31 games started, 14-10, 3.47 ERA, 1.26 WHIP): 34% fastballs, 29% sinkers, 24% sliders, 9% changeups, 4% curveballs. His slider, a good pitch for Coors, was particularly effective (.171 batting average, .286 slugging). He may not fare so well in 2014 with his sinker, though (.250 batting, .359 slugging) given that pitch's Coors performance.
  • Jorge de la Rosa (30 GS, 16-6, 3.49 ERA, 1.38 WHIP): 44% fastballs, 28% splitters, 14% sliders, 7% sinkers, 7% curves. The BP article doesn't reference splitters, but since they rely on a lot of horizontal movement, you'd think they'd fare poorly at Coors. It was OK last year, though (.255 batting average, .358 slugging) and, combined with his outstanding slider (.165 batting, .194 slugging), he seems to have the right arsenal for his ballpark.
  • Juan Nicasio (31 GS, 9-9, 5.14 ERA, 1.47 WHIP): 67% fastballs, 20% sliders, 7% sinkers, 6% changeups. Nicasio's slider is his primary off-speed pitch and he used it far more at home than on the road He's only 27 but his strikeouts were down, his walks up, and his fastball velocity ebbing (average 94.7 mph in 2011, 94.1 in 2012, 92.6 in 2013), so pitch selection doesn't tell the story of his 5+ ERA.
  • Tyler Chatwood (20 GS, 8-5, 3.15 ERA, 1.43 WHIP): 42% sinkers, 30% fastballs, 12% sliders, 12% curves, 4% changeups. Chatwood's go-to pitch is his sinker, which isn't a great pitch at Coors. Batters had a .327 batting average and .467 slugging percentage against it, while is slider had the best results (.183 batting, .217 slugging, and an outstanding 41% rate of swings-and-misses on swings). More reliance on the slider, which he used primarily only when ahead on the count, would help, because that ERA and won-lost record look lucky given his high WHIP.
Predictions based on this: Chacin regresses a bit, de la Rosa doesn't much, Nicasio improves a little provided he isn't hurt, and Chatwood, if he goes to his slider more, is able to avoid some of the seemingly inevitable rise in his ERA.

Incidentally, did you know that in their 21 years, the Rockies have had only seven winning seasons? The only teams (among the 28 that existed in 1993) with fewer are the Orioles, Royals, Marlins, Brewers, and Pirates.

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