Splitsville - Ground Ball Pitchers

by Keith Glab, BaseballEvolution.com
February 1, 2007

Asher recently informed me that Kevin Brown had an ERA more than a full run lower at home than on the road over the course of his career.  I understand that Brown played in pitcher's parks while in the National League, but those that he frequented in the AL were about neutral in terms of run production.  More importantly, Brown was famous for his sinker, and thus not allowing home runs.  Brown's career high in homers allowed was 21 in 230 innings back in 200.  Generally, his seasonal home run totals look like a typical month for Jose Lima.

So it didn't make sense to me that Brown would benefit from pitching in ballparks that depress home runs, as Brown probably wouldn't have given up 25 homers in a season even had he pitched for the Rockies (3 homers allowed in 55 career innings at Coors Field).  Maybe there's something else to consider.

If you spent any time on Baseball Evolution (or even reading Rob Neyer's ESPN column) last summer, you've probably seen me rant about Chien-Ming Wang's home/road splits being affected by the Yankees allegedly softening their infield dirt before home games.  An extreme groundball pitcher like Wang with a lackluster infield defense like the Yankees' would underscore this effect.

Are the Yankees the only team smart enough to employ this tactic?  On a hunch, I compared the career home/road splits of every pitcher who had a groundball to flyball ratio of greater than 2.5 in 2006.  Here is the data, including Kevin Brown's line:

Pitcher (2006 GB/FB) Split Record ERA H/9 IP HR/9 IP
Kevin Brown (N/A) Home 115-66 2.74 8.0 .57
  Away 96-78 3.86 9.1 .57
Brandon Webb (5.09) Home 26-20 3.22 8.2 .72
  Away 21-25 3.35 8.3 .65
Derek Lowe (4.82) Home 61-36 3.37 8.6 .71
  Away 39-46 4.24 9.4 .72
Chien-Ming Wang (4.10) Home 16-5 3.22 8.5 .49
  Away 11-6 4.45 10.3 .66
Jake Westbrook (3.43) Home 30-22 4.10 9.4 .65
  Away 26-31 4.58 10.1 .87
Aaron Cook (3.24) Home 16-12 4.75 10.4 .87
  Away 12-16 4.37 11.1 .54
Roy Halladay (2.88) Home 52-23 3.39 8.4 .78
  Away 43-25 3.85 9.3 .80
Felix Hernandez (2.84) Home 9-7 3.24 7.3 .81
  Away 7-11 4.75 9.6 1.03
Tim Hudson (2.76) Home 59-25 3.26 8.0 .70
  Away 60-35 3.84 9.1 .82

It's hard to look at this table and not notice that every one of these pitchers has a significantly better winning percentage at home.  It is also quite noteworthy that every single one of these groundball pitchers allows fewer hits at home.  Finally, every pitcher listed except Aaron Cook has posted a better home ERA than road ERA in their careers.

This tells me that a groundball pitcher will perform better at home than on the road regardless of his home ballpark.  Aaron Cook, Brandon Webb, and Roy Halladay all have succeed in their hitter's havens while Chien-Ming Wang, Jake Westbrook, and Felix Hernandez all have done fine in their pitcher's parks.

This doesn't make immediate sense.  Coors Field has inflated base hits by 21% over a neutral park over the past three seasons.  Why would Aaron Cook allow fewer hits at home?  Cook actually allowed 15 Coors homers to just two on the road in 2006, but still posted a better home ERA (3.96/4.62) because of his fewer total hits allowed there.        

That's the other item of note.  Aaron Cook and Brandon Webb each gave up more home runs in their home ballparks, which is what we would expect for any pitcher.  Brown, Lowe, and Halladay are about even at home and on the road.  The only surprise there is Halladay of Toronto, whose Rogers Center increased home runs by 20% between 2004 and 2006.  Hudson, Hernandez, Westbrook, and Wang each allowed slightly fewer home runs at home.  Aside from Wang, this goes right in line with each pitcher's home park factors.

This somewhat goes against my intuition regarding ground ball pitchers.  I had always assumed that you would want a sinkerballer to pitch in a home run park, where his ground balls would really come in handy.  As it turns out, groundball pitchers succumb to those park effects in the same way that flyball pitchers do.  It just doesn't hurt quite as much because they allow fewer home runs total.

But look at this table.  Every one of these pitchers is succeeding at home whether they are allowing home runs there or not.  It's the hits allowed that are correlating to success, not homers allowed.

How are pitchers like Cook and Halladay, whose ballparks inflate base hits, still allowing significantly fewer hits at home?  Are their grounds crews watering down infield dirt like the Yankees do?  Are their infielders simply more comfortable with the infield bounces they get on their home turf?  Or do groundball pitchers beat spacious stadiums because they don't allow many fly balls that find empty spaces between the outfielders?

It's probably some combination of the three.  In any case, a groundball pitcher is going to succeed at home no matter what.  However, it's probably wiser to stick a groundball pitcher in a cavernous hitter's park that inflates singles and doubles than in a tiny bandbox that inflates homers.

What does this mean in our evaluation of Kevin Brown?  His splits are still more extreme than many of the other pitchers on this list.  Yet to some extent, we should expect this disparity between his home and road numbers.  Like Nolan Ryan, an extreme strikeout pitcher, tossing mostly in pitcher's parks probably did not help his ERA much at all, but doing so certainly had an adverse effect on his ERA+.  That's got to be kept in mind when we compare him to other pitchers in those categories.

It's not Kevin's fault that the Dodgers made him the highest paid player in the National League for four years when many other pitchers would have benefited more from pitching in Dodger Stadium.     

Disagree with something? Got something to add? Wanna bring up something totally new? Keith resides in Chicago, Illinois and can be reached at keith@baseballevolution.com.