It's official: Koji Uehara is headed to the bullpen. I happen to think he will perform very well in this role, mainly because he pitched fairly well as a starter last season. Brittany Ghiroli also makes another point: he pitches much better the first time through the batting order. Then again, so do all starting pitchers. Koji, though, is extreme:
|tOPS 1st||tOPS 2nd||tOPS 3rd|
tOPS is simply the OPS allowed relative to a player's (or the league's) normal. So if a player performs at 100, he is performing at his average level. Below 100 for pitcher, means he pitched better than his normal.
As you can see, all pitchers tend to perform more poorly as they advance through the game; this is part of the reason why pitchers post better numbers as relievers than as starters. You can also see that Uehara's splits were far greater than the rest of the league. If he pitches out of the bullpen like he did his first time through the order (.202/.224/.337 with a 9:1 strikeout to walk ratio), the O's will have a shut down reliever.
(I apologize for the looks of that table; I'm very, very rusty on my html.)