Earlier today, Buster Olney tweeted, "A couple of scouts say this: they saw Wainwright's arm angle dropping down the stretch last year, a sign of trouble."

Jeff Sullivan examined the claim over at SB Nation and found no evidence to support it. I thought I'd check my corrected PITCHf/x release point data to see if I could find anything that Jeff might have missed by working with uncorrected data. Not really—I agree with Jeff.

This graph uses the technique outlined here and presents two dimensions of Adam Wainwright's release point over time.

Wainwright release point 2008-2010

Wainwright did drop his arm angle on May 16, 2009, but it's been pretty constant since then, according to PITCHf/x data.  There were some minor variations throughout 2009 and early 2010, but from June 9, 2010, Wainwright's arm angle was very consistent. He did begin in June the process of moving over about six inches toward the first base side of the pitching rubber, but his arm angle stayed consistent throughout that time.

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Great stuff, Mike (and Jeff). I'll be impressed when Buster can find scouts who can consistently predict which pitchers are GOING to get hurt. It's a confirmation bias - post hoc ergo propter hoc double play!
Funny how data can disprove those cute little stories that pervade baseball journalism.
Isn't the horizontal shift here consistent with the scouts' observations? I don't know what a horizontal shift in release point looks like on a real arm and shoulder, but in 132 characters or less, could it be that "arm angle dropping" is a quick and dirty way to describe it?
No. If you're a right-handed pitcher, as Wainwright is, when you raise your arm angle, the vertical release point rises and the horizontal (left/right) release point moves toward first base. If you drop your arm angle, vertical release point drops and the horizontal release point moves toward third base. If the vertical release point stays constant and the horizontal release point changes, then the pitcher is shifting on the rubber without changing his arm angle. If a pitcher both changes his arm angle and moves on the rubber at the same time, the result in the horizontal dimension can be more complex (sum of the two effects). However, if the release point doesn't change in the vertical dimension the pitcher can't be changing his arm angle, unless he's coming basically overhand to start with, which Wainwright definitely was not. You can stick your arm out at a 45-degree angle and see for yourself how the release point changes in each dimension when you raise or lower your arm angle.
This is why I subscribe to BP and don't follow ESPN on twitter. Excellent work.