Who was the Braves' best right-handed reliever other than Craig Kimbrel in 2012? Okay, it's a bit of a trick question, since the answer is "Kris Medlen." He may have spent part of the year in the rotation, where he dominated, but he was easily the Braves' most effective righty setup guy, too.
Okay, but who was the Braves' third-best righty reliever? There are really only two other options: Cristhian Martinez and Chad Durbin. Both spent the entire year with the club and both pitched well at times. If you look just at bottom-line numbers like ERA and Win Probability Added (WPA), you'd get the idea that Durbin pitched much better than Martinez:
- ERA: Durbin 3.10, Martinez 3.91
- WPA: Durbin +0.96, Martinez -0.54
These stats imply that Durbin was an above-average (if hardly spectacular) pitcher while Martinez was below average (though not terrible). If you look at their peripherals, though, you get a completely different picture:
- K Rate: Durbin 19%, Martinez 21%
- BB Rate: Durbin 11%, Martinez 6%
- HR Rate: Durbin 3.5%, Martinez 1.9%
- FIP: Durbin 4.78, Martinez 3.16
Compared to Durbin, Martinez struck out more, walked (a lot) fewer, and gave up fewer home runs. That's why Martinez has a solid Fielding Independent Pitching mark while Durbin has an awful one. Simply put, their peripherals suggest that Martinez was a bit unlucky in 2012, while Durbin was incredibly lucky.
These two players' 2012 statistics make for a great case study in the need to look deeper when evaluating relievers. ERA is erratic from year to year even among starters, so when you're evaluating players who pitch 1/3 as many innings, ERA is all but useless for projecting future performance.
Looking just at ERA, you'd say that the Braves should try to re-sign the free agent Durbin, and that they should even consider non-tendering the arbitration-eligible Martinez. Even a quick peek at the peripherals, however, warns that Durbin is liable to implode next year and that Martinez is likely to be a bargain at around $700K in salary.
That's not to say that Durbin was actually bad in 2012. In fact, I think it's indisputable that he was an asset. It's hard to argue with that WPA. But here's a pitcher who has been a full-time reliever for 5 seasons now and has three times had a FIP above 4.75. His ERAs have vacillated wildly: 2.87, 4.39, 3.80, 5.53, 3.10.
Durbin just is not a guy you can count on having two solid years in a row. He was worth a $900K flyer coming off a bad 2011 season, and that paid off for the Braves. But now that he's coming off a (superficially) better year, he'll likely command a bigger salary, and the chances are not high that he'd be worth that kind of money.
As for Martinez, he seems like your prototypical middle reliever. He'll never knock your socks off, but he'll put up solid enough numbers that you like having him on your team as long as he doesn't have to pitch high-leverage innings. Until his arbitration price gets too high, he's a nice value.
Regardless, I think the Braves need to add at least one more righty reliever for 2013. Having Cory Gearrin up for a full year could help, but the Braves still need more right-handed bodies. Relievers are hard to predict, but if you have enough of them, some are bound to work out. Fortunately for the Braves, most relief arms can be had relatively cheaply.