The Braves' pitching staff has floundered a bit since the All-Star Break. So let's take a minute and go through all the starters' peripheral numbers to find out what's up, and what may be in store for the remainder of the season.
Jair Jurrjens - Currently sitting on the disabled list, it's not necessarily clear what version of Jair Jurrjens we will get upon his return. Jurrjens has consistently puzzled sabermetric types due to his apparent "weak contact" peripherals without any immediately recognizable cause like a knuckleball or, I don't know, covering the ball in chewing tobacco.
We now have almost four years of major league data to analyze on Jurrjens, and the picture's still not quite clear at the moment. In 2008 and 2010, Jurrjens put up ERA numbers (3.68, 4.64) just a bit over his FIP numbers (3.59, 4.19), not a shocking result given the Braves' generally poor defense backing him up in a neutral home park. However, 2009 and thus far 2011 have produced almost identical results that bend a mile in the opposite direction, with a FIP of 3.68 and 3.69 somehow leading to an ERA of 2.60 and 2.63.
How is this confusing? Jurrjens doesn't strike out a ton of guys (5.72 per 9 innings gets you nowhere on a league leaders list that includes Tommy Hanson at 9.83 per 9 innings) and while his walk numbers are pretty low, they aren't special enough to explain his success, either. Sabermetric statistics don't believe that a pitcher can really control what happens once the hitter manages to put the ball in play, but that seems to be just what's happening with Jurrjens.
Opponents' batting average on balls in play (BABIP) is a low .263, and in Jurrjens' other successful year in 2009, it was a similar .268. In his off years of 2008 and 2010, the BABIP against him was .301 and .300. So now we're getting somewhere, we have a very light correlation. BABIP is usually equated with luck, and while that is true in Jurrjens' case to some extent, he also has some characteristics of a consistent weak contact pitcher. Hitters facing Jurrjens have hit a home run only 7.3% of the time they hit a fly ball of any type against Jurrjens over his career, where the standard expected rate is 10.5%. That's not luck, it's something else. Even in 2010, hitters only managed to hit 8.8% of their fly balls out of the park against him.
But yes, Jurrjens has been a bit lucky this year. He's left a career-high 81.9% of opponent runners on base, compared to 69.3% last year. If you don't believe in clutch pitching, that means he's been pretty lucky. If you do believe in clutch pitching, then, well, Jurrjens is finally becoming clutch in his fifth year in the big leagues!
Tommy Hanson - Thankfully for this article's word count, no one else on the Braves staff is nearly as complicated as Jurrjens. In fact, Tommy Hanson is basically the opposite of him in sabermetric understanding. Hanson's ERA is consistently right along there with his FIP (career ERA: 3.28; career FIP: 3.46) and he's a high strikeout guy who shouldn't have to worry about his defense as much as almost any pitcher out there right now. But this has quite suddenly become a marginally disappointing year for Tommy as he sports a 3.60 ERA on the season despite a wafer-thin .216 batting average against and the league's third-best strikeouts per nine numbers.
Every one of Hanson's peripherals have improved this year except one very important one that you can probably already guess, having seen him pitch: home runs. His home run per fly ball ratio has sprung up from about 6.3% to 12.5% this year. Why? Well, he's been a little unlucky, but he's also hung too many curveballs high in the strike zone. Braves fans have to just hope he gets over that tendency, wherever it came from
Brandon Beachy - Take what I said about Hanson and apply it to Beachy. He's a strikeout pitcher who's been giving up more home runs than you'd expect, but unlike Hanson, he's managed to cover that problem up by leaving more men on base than you'd expect.
Derek Lowe - Derek Lowe has well-documented stamina issues. His only other issue was that one DUI. It is perhaps possible that a stamina problem and an alcohol problem may be related.
Tim Hudson - Hudson had a very, very successful year in 2010, overcoming a below league-average FIP for the whole season with very high LOB% and very low BABIP. This year, his peripherals say he should be doing significantly better than last year, but his luck has been remarkably average, so it just looks like an okay year. There's nowhere to regress to, Hudson is having exactly the year his peripherals suggest he should be having.
Mike Minor - We clearly have a smaller major league sample size on Minor this year, but over his seven starts, it would appear he's been very unlucky, unless something about his pitching happens to lead to a bunch of line drive hits and yet zero home runs. Yes, Minor has yet to give up a home run this year, but opponents have a .357 BABIP against him and he's left a lower rate of men on base than any other Braves starter. The only bad sign is that over his 8 major league starts last year, it was the same story: high BABIP against leading to a remarkably high ERA for what it should be. Probably just a small sample size problem, given his performance in the minor leagues.