After reading Tim's interesting piece over at PP on the Pirates' collection of ground ball pitchers and infield defense and connecting it with something Brian Cartwright said about park effects the other day, I was curious to see if there were any signs of a grand plan in place that was allowing our pitchers to outperform their FIP's, or if we're just looking at some noise. I looked up a couple stats on Fangraphs and thought I'd share what I found. I rolled up all Pirates pitchers and hitters and looked at the home/away splits and got the following.
Home: 3.47 xFIP, 3.19 FIP, 2.49 ERA, .251 BABIP, 23.9% K, 8.9% BB, 8.3% HR/FB
Away: 4.06 xFIP, 4.33 FIP, 4.08 ERA, .280 BABIP, 19.5% K, 9.4% BB, 13.3% HR/FB
Home: .291 BABIP, 19.8% K, 7.3% BB, 9.2% HR/FB
Away: .286 BABIP, 23.6% K, 7.4% BB, 14.4% HR/FB
A couple things. First, you can see park effects directly, specifically showing how PNC suppresses HR's for both teams. Secondly, you can see where home field advantage comes from: umpires giving more strike calls (and thus K's) to the home team (there are articles on this out there, but I'm too lazy to look them up). The batted ball profiles (not shown) are pretty similar for home and away, so the xFIP and FIP splits are probably pretty close to what you'd expect to see.
Now for something we might not expect: on the road the Pirates ERA and xFIP is almost identical, but there's a full run difference at home. The .280 away BABIP is a little low, but for the reasons mentioned in Tim's article, with ground ball pitchers and some good defense, it's not out of the question that we could sustain something like this. The .251 home BABIP is very low and probably not sustainable, but it is an open question whether there is a good reason for the disparity or not.
I would have liked to look at the BABIP splits for different types of batted balls, but that information is not readily available on Fangraphs and I wasn't prepared to put more effort into it than that. It would be interesting too look at it if someone else had an easy way of finding this information.
The fact that our hitters have a higher home BABIP than away BABIP counteract suggestions that it's due to a park effect (e.g., maybe the grass at PNC is covered in glue!), and actually, I ran the BABIP numbers from 2001-2012 and found that both the Pirates and the opposing team had a 0.08 difference between their hitters home BABIP and away BABIP. I wasn't aware of this phenomenon, but it makes some intuitive sense that fielders can field better on their home turf and/or hitters in better counts (due to fewer strike calls) make better contact and have a higher BABIP. One other curiosity is that last year, both the Pirates and the opposing team had lower BABIP's at PNC than at other parks. Below are the data I collected which show a lot of variance from year to year and no clear trends.
(My browser won't let me make tables, sorry!)
Year | Pirates H-A BABIP | Opponent H-A BABIP
2013 | 0.005 | 0.029
2012 | -0.021 | 0.032
2011 | -0.018 | 0.004
2010 | 0.014 | 0.027
2009 | 0.019 | 0.023
2008 | 0.002 | 0.008
2001-2012 | 0.008 | 0.008
So what conclusions can we make? I'm pretty skeptical that NH and co. have uncovered some secret low BABIP sauce, but it's worth keeping an eye on. If we break down the splits, most of the behavior is fairly well explained by previously observable phenomena and/or variance. Some of it could come down to the improved defense (maybe Marte is the shiz in PNC but wasted somewhat in smaller left fields?) and defensive shifts. Maybe pitch framing is so powerful it can lower opposing BABIP's, increase the velocity of projectable pitchers, prevent injuries during Navy Seal training, and help free agents want to come to Pittsburgh. One way or another, though, we need a longer track record of it before we could say it's predominantly something other than variance. I don't think it's an open and shut case and there are more ways to slice and dice the data than what I've done here. I'd be interested to see what others think, what related research is out there, and whether there are any other observable patterns in the stats that could hint at competitive advantages and the sustainability/unsustainability of our pitching.