What's really wrong with Joba?

Anybody else notice a significant decline in the speed of Joba’s fastball over the last year and a half? Joba Chamberlain burst onto the scene in 2007 with a fastball averaging over 97 MPH according to the PitchFX charts at Fangraphs touching 100 MPH on occasion.

The graph below from Fangraphs shows how for most of 2008 his fastball was still pushing the 100 MPH mark. He began 2008 in the bullpen picking up where he left off in 2007 by punishing hitters whenever he came into the game.

Then the transition began to convert him to a starter. In the beginning, he was impressive as a starter also. Though his innings were limited to around 5 per game when the infamous “Joba Rules” were put into effect. Then, toward the end of the season he was forced out of a game in Texas and was shut down for a few games with shoulder tendinitis. Since then his average speeds have come down and we haven’t seen him consistently come close to those higher speeds again. So did this mid year transition ruin Joba either mentally or physically?

Something changed. For all of 2009 he was a starter and the stats show that the average speed of his fastball declined to under 93 MPH. We saw occasional glimpses of a dominant starter but nothing consistent. He was converted to the bullpen for the playoffs and did make a contribution in that role. But we still didn’t see the dominance and those pre-August 2008 speeds again.

Lets say he holds back as a starter in order to conserve energy to pitch most of the game, and that explains the lower average speeds. But if that was the case, why didn’t he bring back the 97+ MPH fastball for those relief stints in the post season? The Joba Rules limited his innings so he should still have had something left in the tank. He knew he would only throw an inning at most each game. Surely the adrenaline alone should have had him pushing 100 MPH in the World Series. It's early but so far in spring training we haven't seen much of a change from 2009.

So what’s up? Are the Joba Rules or the debate about whether he should be a starter or reliever messing with his head? Could the success have affected him? Maybe he isn’t working hard enough to stay in shape like he was when he first came up. Is he now being affected by that lack of time in the minors? Or has he never been able to fully recover after walking off the mound in Texas? I'm not sure what it is, but let's get the guy with the 97 MPH+ fastball and that wicked slider back. That's the pitcher the Yankees need Joba to be. But will we ever see him again?