Earlier in the season Dave Cameron asked me what to make of Ben Sheets‘ release points. Sheets has two distinct release points: check it out. Dave wanted to know whether that was a real difference or some noise in the pitchf/x system. Release points are not directly measured by the pitchf/x system, but placed some constant distance away from the plate (the default is 50 feet) along the trajectory of the pitch. This means they are not perfect, but a pattern of such distinct clumps is usually a legitimate phenomenon and not just noise.
Sheets’ clumps were noted over at Athletics Nation where danmerqury suggested they were due to different arm angles (you see that with Jose Contreras where the different clumps of release points correspond to different arm angles). But in this case it is something else as Mike Fast offered great visual evidence (make sure to click through and see what Mike posted) that Sheets is shifting on the rubber based on the handedness of the batter. Here are Sheets’ release points this year color-coded by RHB v LHB.
So Sheets shifts to the catcher’s left (Sheets’ right) against LHBs. I think this allows him to keep his pitches away against LHBs even if they have the same movement and trajectory. Sheets throws the occasional changeup, but most of the time it is either his fastball or his curve (between the two they make up over 90% of his pitches). Here are the trajectories of four of his pitches from last night. A curve and fastball to Jorge Posada (batting lefty) and a curve and a fastball to Alex Rodriguez.
His two fastballs (in green)
have about the same movement and trajectory, but because they are thrown from a different starting point they both end up away both end up away, at least partially because of how Sheets shifts over against Posada. Remember LHBs stand to the right of the zone and RHBs to the left because the image is from the catcher’s perspective. The two curves have slightly different movement (this is not consistent across his curves to RHBs and LHBs just happened with the two I choose), but I think the shifting also helps him keep his curves away to all batters.
Mike Fast noted Trevor Hoffman as another guy who shifts on the rubber based on batter handedness. Do you all know any other pitchers who do this?
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