Here's a Thought: Washington Nationals' Sean Burnett on Shaky Ground

The Nationals acquired Sean Burnett from the Pittsburgh Pirates during midseason 2009 and were rewarded with a 3.20 ERA down the stretch. Burnett also posted a 3.06 ERA with Pittsburgh prior to the trade, so his ERA for the year was 3.12.

Given those numbers, it would seem that the former top prospect has settled in nicely as a middle reliever, but upon closer inspection, that's not the case.

Burnett had the lowest BABIP of any pitcher in the majors who threw at least 50 innings last year at .201. Ironically, the pitcher he was traded for, Joel Hanrahan, had the highest at .392.

Indeed, when you look at Burnett's other statistics, they don't look like those of a three-ish ERA pitcher. 43/28 K/BB ratio? Meh. A HR/9 of .94? OK, I guess. But those look more like the numbers of a serviceable, 4.5-5.0 ERA pitcher than one with a 3.12 mark.

I wondered if there was some reason Burnett's BABIP was so low. Earlier this month, I found that the one other pitcher with a .201 BABIP (Astros lefty Tim Byrdak) had done an excellent job limiting liners and actually deserved one of the lowest BABIPs in the majors (.277, which is still far higher than .201). 

There's certainly nothing in Burnett's track record that portends a .201 BABIP—he had a .309 mark as a 2004 rookie and a .298 one in 2008. 

Worse news than that is that Burnett actually gave up more line drives in 2009—20.8 percent—than he had in either of his previous years. That's slightly worse than average, and leads to a slightly worse than average .321 xBABIP.

A .120 difference.

The difference between Burnett's xBABIP and his BABIP is staggering—to put it in context, it's a whopping 35 points ahead of Phil Coke's second-place .085, and the highest difference in the other direction was Russ Springer's -.071.

So Burnett was picked up by his defense more than any other pitcher in baseball, in terms of simply taking away hits and turning them into outs. 

Not surprisingly, Burnett is high up on the True ERA/ERA difference list, coming in at 13th with a 1.87 run difference between his 3.12 ERA and 4.99 True ERA. He's really just a borderline second lefty/groundball specialist at this point, not an upper-echelon lefty reliever. 

Here's hoping the Nationals notice Burnett's 2009 luck and don't hand him a lot of high-leverage innings in 2010.