Yesterday, I attempted to argue in simple terms that Mike Pelfrey is a good candidate to bounce back sometime soon — using nothing but strikeouts and ERA, basically. Simple stuff. Reader-person David, in the comments section hereabouts, made a good argument that there are some things to worry about with Pelfrey that go beyond that, and maybe he won’t bounce back. Let me just quote him here:
His GB% and FB velocity have declined. Last year, he admitted to pitching hurt. Pitchers who don’t miss bats tend to fall apart quickly (CM Wang). Freddy Garcia is making 1.5M and he has an identical xFIP to Pelfrey.
Frankly, I think his downside is worse than his upside (3 WAR pitcher) at this point.
Good points. I countered, since we entered the world of advanced metrics, that Pelfrey’s SIERA (allegedly the most accurate future-ERA predictor) is a career low this season, and his fastball velocity declined from 2009 to 2010 and Pelfrey pitched better in 2010 anyway.
But that’s not really the point of this post. The point is that this got me thinking about fastball velocity, specifically declines in fastball velocity and how they affect pitchers. In 2010, Mike Pelfrey’s fastball averaged 92 MPH; this season it’s down to 91.5 MPH. Breaking it down further, his four seam fastball has dropped from 92.0 MPH to 91.4 MPH, while his two seamer has fallen from 91.7 MPH to 91.4 MPH. So he’s looking at a drop in 0.6 MPH on one pitch and a drop of 0.3 MPH on another. For the sake of this argument, we’ll assume that these declines are actually happening, and it’s not just pitch f/x registering his slower, not-sinking sinkers as four seamers (which I think has happened sometimes) or some other mishap on occasion this season.
I don’t know what a drop in velocity means, but thankfully, someone has already looked into this stuff. Last year, Mike Fast wrote an excellent piece for the Hardball Times about declines and increases in fastball velocity. You should check it out, but to quote a small part of Fast’s conclusion:
. . . a starter’s run average would increase by about 0.25 for every mph lost off his fastball, and 0.45 per mph for a reliever.
Pelfrey has lost less than a full MPH off his fastball, and let’s just go with the 0.6 MPH figure that’s fallen off his four seamer. Going with one MPH equals 0.25 runs per nine inning, that figure works out to a 0.15 rise in Pelfrey’s run average per nine innings, which should be a little less than 0.14 rise in his ERA. A 0.15 rise in his run average, over 200 innings, works out to three extra runs. Even if you figure a slight decline in fastball velocity affects Pelfrey twice as much as a normal pitcher, that’s just six runs over 200 innings, and his ERA should only rise 0.28 runs. Pelfrey’s ERA is a full run higher this season than last season.
Rhetorical question time: Does fastball velocity matter? Of course. Are declines in fastball velocity good signs? No. But I don’t see how a 0.6 MPH decline in Pelfrey’s fastball velocity explains much. Jered Weaver’s velocity has dropped 0.4 MPH this season; his ERA is a full run lower. CC Sabathia’s fastball velocity is down 0.8 MPH since 2009, and he’s having arguably the best season of his career. I see how a drop in velocity probably explains some of Pelfrey’s struggles this season, but it’s not as worrisome as his inability to get good sink on his two seamer:
Where Pelfrey threw his sinker to righthanded batters, 2010 (catcher’s view):
Where he has thrown his sinker to righthanded batters, 2011(catcher’s view):
Red is where a lot of pitches go, blue is where fewer go. I’m going to assume that low and inside is the happy area, and square in the middle of the plate is bad. Pelfrey has a lot of sinkers in the middle of the plate both seasons, but almost no low and inside pitches this season, which explains the home runs, the low GB%, ect. His sinker just isn’t sinking, and that’s the biggest part of his struggle. Fastball velocity matters for Pelfrey, but I don’t think anywhere near as much as movement — and it’s not like he’s lost four MPH or three MPH or even one MPH. He’s lost 0.6 MPH. It’s all about the sink, and I think he’ll figure it out and pitch better.