The Orioles brought Koji Uehara back on a one-year contract last season, making him the team's best reliever but (1) not giving him the closer's job (he totaled exactly 0 saves) and (2) giving him less money than Kevin Gregg got.
Koji rewarded the team by not only staying healthy, but being his usual awesome self, posting a 1.72 ERA, 2.56 FIP, and 2.45 xFIP. Uehara struck out 11.9 betters per nine, while only walking 1.5 for the Birds - the man would be nearly unbeatable if he didn't give up so many flyballs (and, therefore, home runs). That last part was an issue after he was dealt to Texas - in a move that gave the O's good value but which I didn't like in principle- as his home run per flyball rate more than doubled to 25% and he gave up a homer about every 3-4 innings. Still, with his 23 K:BB ratio for the Rangers (not a typo - 23!), his xFIP there was 2.03 despite an ERA over 4.
I wrote about Koji's ability to generate whiffs despite only throwing 88-89 mph earlier in the year - you can check that out here - and it really is amazing. Heck, it's allowed him to post the best strike-out to walk ratio in the history of baseball* at 7.23 (and that's by a fair bit too - second place is 5.63).
* Since 1890, min. 100 career IP.
It was unfortunate that Koji was left off Texas' roster for the World Series, as watching him pitch was one of the fun parts of being an Orioles fan in recent years - and though I didn't want the Rangers to win (or the Cardinals, frankly), it would have been nice to see him get a ring. With his innings threshold crossed, the $4 M vesting option for 2012 was picked up so it looks like (barring a trade) Uehara will be staying in AL West for a full season. If he remains just as effective as he was this year though, I'd be open to bringing him back to Baltimore for 2013 (as long as he's cheap and doesn't require giving up a draft-pick to sign, of course).