Josh Beckett and DIPS Theory

Last year, Josh Beckett posted a 5.78 ERA in 21 starts, and his struggles were one of the main reasons the Red Sox missed the playoffs. This year, Josh Beckett has a 1.86 ERA in 14 starts, and his dominance is one of the reasons that the Red Sox have the best record in the American League. A look beyond ERA, however, shows that Beckett is the poster boy for why metrics like xFIP were created in the first place.

Last year, Beckett had an xFIP of 3.86, 8% below league average. This year, Beckett is posting a 3.69 xFIP, 8% below the league average. In fact, his K/BB ratio is almost exactly identical (2.58 last year, 2.63 this year) to what it was a year ago. His ERA has been slashed by over four runs thanks to huge reductions in two factors that are counted in xFIP – BABIP and HR/FB.

Last year, Beckett had the third worst BABIP (.338) of any starter who threw at least 100 innings. Only Brandon Morrow and James Shields were worse, and Aaron Harang posted the same mark over in the National League. In addition, Beckett posted the fourth worst HR/FB rate in the majors, behind only Jorge de la Rosa (who pitched in Colorado), Manny Parra, and Kevin Correia. Beckett gave up a lot of hits and a lot of home runs, and that’s a lethal combination for a pitcher’s ERA, even if he’s not walking guys and racking up a decent amount of strikeouts.

This year, Beckett has the lowest BABIP (.217) of any starter in baseball, and his 3.9% HR/FB rate is the fifth lowest of any qualified starter. He’s regressed right past the mean, and now his performance in 2011 is as unsustainble as his 2010 performance was, just in the other direction this time. Just like Beckett was a great pick to improve upon his struggles last year, he’s a good bet to regress in the second half of this year.

I know it’s tempting to look at guys who have both high BABIPs and HR/FB rates simultaneously and assume that they must be doing something wrong that allows hitters to tee off on them with regularity. Last year, we had this same conversation about Dan Haren after the Diamondbacks got tired of a “too hittable” pitcher and shipped him to the Angels. At the time of the trade, Haren had a 3.19 xFIP, but his ERA was 4.60 thanks to a .336 BABIP and a 13.9% HR/FB rate. Upon arriving in Anaheim, those numbers immediately dropped, and have stayed below the league averages ever since.

Beckett (and Haren, and James Shields, and many of the other names on the list of guys we noted who were hit hard last year) are seeing dramatically different results this year than they did last year. In a few cases, they are pitching better, though the improvements aren’t anywhere close to the same scale as ERA would suggest. Beckett, though, looks to be almost exactly the same pitcher as he was a year ago, just now he’s on the other side of the results fence.

If you look at Beckett’s 2010-2011 data as one complete season, as he’s started 35 games since the beginning of last year, his line for that “season” has him putting up a .292 BABIP and a 9.8% HR/FB rate, almost exactly average in both categories. For his career, Beckett has right around average marks in both categories.

Besides the sequencing, there’s nothing all that weird about the last 35 starts of Josh Beckett’s career. He had a run of bad luck and a run of good luck, but they’ve nearly canceled each other out, and over the course of 220 innings, his line looks to be pretty close to what you’d expect given his underlying walk rate, strikeout rate, and batted ball stats.

Josh Beckett was never terrible, and he’s not amazing now. More than anything else, he’s an example of why ERA isn’t a good tool for projecting future pitching performances.