Tommy Hunter was traded to the Orioles in July 2011 along with Chris Davis for relief pitcher Koji Uehara, and while Davis has turned out to be the real jewel of that trade, Hunter has proven himself a valuable member of the O's bullpen.
In the final month of 2012, Hunter was sent to the bullpen for good and it may have been the best thing that could have happened for his career. In September 2012 Hunter pitched 12 2/3 innings and allowed just one run as batters hit just .255/.280/.298 against him. He went from a meh starting pitcher to a flame throwing, shut down reliever and going into 2013 it looked like he'd be a very big part of the bullpen. He was.
As a starting pitcher, Hunter's average fastball velocity was just about 90 and in 2012 was worth -19.4 runs above average. As a relief pitcher in 2013 he dialed up an average velocity of 96 (touching 100 on occasion) and for the season the pitch was worth 16.3 runs above average. He was basically a completely different pitcher once he made the switch to a reliever.
One thing Hunter has always been prone to do is give up home runs (and he knows it, having given himself the Twitter handle of @TommyGoesBoom), and while he did still struggle with it at times in 2013, he cut his HR/9 rate in half from 2012 to 2013 (in 2012 it was an almost unbelievable 2.2 home runs per nine). Unfortunately for the Orioles, Hunter tended to give up home runs in big situations. Seven of the 11 home runs he gave up either tied the game or gave the other team the lead, and five of those home runs were in the 9th inning or later. One of them was to Toronto Blue Jay Munenori Kawasaki, the only home run he has ever hit in either the major or minor leagues.
Yes, Tommy definitely got known as the guy who gives up homers in big situations last year, but a lot of that had to do with the fact that he pitched in so many high-leverage situations in the first place. Other than closer Jim Johnson, Hunter and Darren O'Day were the main go-to guys for big spots.
When I remember Hunter's 2013 season, I will probably remember the game-ruining home runs. But objectively I don't think that's fair to him, though, because he really did have a very good season. He was especially devastating to right-handed batters, who hit just .141/.190/.154 against him. His big trouble was lefties, as it has been throughout his career. In fact, all 11 home runs he gave up were to lefties. When Adam Dunn walked off against Hunter on July 4th I remember saying before Dunn even came to bat, "Buck has to take Tommy out before Dunn, right?" Buck didn't, and Tommy went boom.
I think his issues with lefties are consistent enough that he shouldn't be facing them regularly, especially those with power like Dunn and Robinson Cano. Somehow Hunter faced lefties in 2013 more often than righties (my assumption is that often pinch hitters were sent in, though that kind of data culling isn't on my to-do list), which needs to change going forward. Lefties slugged .535 against him in 2013 and have slugged .500 over his career.
Even with those troubles, Hunter was a valuable member of the team and will continue to be (especially if they stop letting him get knocked around by lefties). Baseball Reference assigned him a WAR of 2.0, tied with O'Day for tops in the bullpen. He had a WHIP of 0.985 and a K/BB of 4.86. He allowed just four of 28 inherited runners to score.
Hunter is entering his second year of arbitration after earning $1.82M in 2013. He's due for a decent raise, but probably not nothing that will break the bank (after all, he didn't rack up 50 saves). He'll be a free agent in 2016, and while I don't think the Orioles will trade him, it'd be interesting to see what he might be worth. He came to the O's a mediocre starting pitcher and he is now a shutdown relief pitcher with two years until free agency. The thought is that relief pitchers are often worth more at the trade deadline but presumably the Orioles will be in contention (or pretending they're in contention) at that time and so it wouldn't make sense to deal him. It may not make sense in the off season either depending on how you perceive his value. He, Johnson, and O'Day will most certainly have similar roles in 2014 and could be a solid backbone for the 'pen.