After yesterday's game, the Star Ledger's Marc Carig noted on Twitter that A.J. Burnett had shifted towards the third base side of the rubber in order to get a better angle to the plate. The chart below, with "release" indicating the location of the ball at 50 feet from home plate, confirms this:
Only 2011 home games were used in order to limit the amount of park calibration variation. You can see that his most recent start is a big horizontal release outlier, as he's shifted about a foot towards third base (or "negatively," since this is from the catcher's perspective) from where he usually is.