In major league history, no pitcher has had a debut quite like Craig Kimbrel's. Come to think of it, no pitcher has ever had a season quite like Kimbrel's 2010. And I mean that as both a huge compliment and a slight insult.
What made Kimbrel's 2010 season so special? To begin with, he had a miniscule 0.44 ERA, the 4th-lowest debut ERA of all time (for relievers with 20+ IP). That works out to one earned run in 20.2 IP (he also gave up an unearned run).
That low ERA does not tell nearly the full story, however. Kimbrel also gave up only 9 hits, good for fewer than 4 hits per 9 innings (3.92 to be exact). That’s the 7th-best hit rate of all time (again, 20 IP minimum). He gave up no home runs, which is obviously hard to beat. Hitters hit only .125 off of Kimbrel, and slugged only .153 (4th-best all-time). Oh, and 3 of those 9 hits were of the infield variety, so he only gave up 6 "true" hits.
Kimbrel’s success in limiting hits was not the result of crazy BABIP luck, either. His BABIP was .282, which is a bit below expected but not ridiculously so (FanGraphs has his BABIP at .330, but from what I can tell, that is just wrong). To put it simply, batters couldn't get hits off of Kimbrel because they couldn't even put the ball in play to begin with.
That leads us to Kimbrel's specialty: the strikeout. He struck out nearly 2 batters per innings: 40 K in 20.2 IP (17.42 K/9). That sounds pretty impressive, but it’s actually extremely> impressive. Kimbrel's strikeout rate is the highest of all time for any pitcher with 10 or more innings pitched. Seriously. He even outdid Carlos Marmol, whose 15.99 K/9 this year set the record for all relievers with more than 30 IP. When you have outdone Marmol in the strikeouts department, you have done something pretty remarkable.
Unfortunately, Kimbrel also outdid Marmol in the walks department, which is nearly as difficult. Whereas Marmol walked "only" 6.03 batters per 9 innings, Kimbrel's figure was 6.97 BB/9. That's not historic (this year alone, Jordan Norberto of the Diamondbacks had a 9.90 BB/9 mark: 22 BB in 20 IP), but it is very, very high. Kimbrel may have to take his fastball down a half-notch in exchange for better control if he wants to be a major-league closer (though Marmol makes it work most days, so who knows).
One piece of comfort for those who worry about Kimbrel's control is that he seemed to be less wild in his last two stints with the big club, starting in late August. From then until the end of the regular season, he walked 6 men in 12.1 IP, or 4.38 BB/9. That figure is still high but much more workable—and certainly better than the 10 BB in 8.1 IP he had in the first half. What's even better is that as Kimbrel's control was improving, he didn't lose his ability to strike guys out. In fact, his K/9 actually went up, from 16.2 to 18.2. Not coincidentally, Kimbrel did not give up a single run during this stretch.
Looking ahead to 2011, Kimbrel seems to have a very good chance to become the Braves' closer. We know the Braves like his potential in that role, and it would be fitting to replace Billy Wagner with the "right-handed Billy Wagner." I'm sure there are some concerns about Kimbrel's inexperience, but seeing as how his main competition (Jonny Venters) is also entering his second season, I don't see experience as the deciding factor.
If Kimbrel does win the closer's role, and if he is even close to as dominant in 2011 as he was in the last month 2010, he will be a very strong contender for Rookie of the Year. Not to mention that the Braves will have a fantastic closer. Kimbrel's success is far from assured, but one thing is certain: he'll be interesting to watch.