Rob Neyer of SB Nation has an interesting post on a column Bill James wrote for Bill James online, where James sort of suggests we're all overrating groundball pitchers a little bit. Here's the link to Rob's piece, and the link to Bill's original piece (subscription required).
One of Bill's arguments is that almost all the best pitchers -- in any generation -- are fly ball pitchers, and that groundball pitchers seem to get hurt. Especially the extreme groundball guys, like Brandon Webb or Chien-Ming Wang, with Derek Lowe being an obvious exception in that category.
What complicates this issue is how you categorize different pitchers. Do you count groundballs (or fly balls) as a percentage of all outs recorded, including strikeouts? Or do you simply compare groundball outs to fly ball outs (and what do you do with line drives)?
Anyway, after conducting a study, Bill writes:
I think that the advantages of throwing ground balls have been horribly overstated, and that the best way to get batters out is to find pitchers who can throw high fastballs. However, throwing ground balls does appear to be a small advantage for the pitcher, if you control for the number of strikeouts. Given two pitchers with the same strikeout rate and the same walk rate, it does appear that we should favor the one who gets more ground balls, although this advantage is probably no larger than the advantage of being a good fielder or the advantage of having a good move to first.
Of course, if there's a debate here, I don't think it's between two pitchers with the same strikeout rate. To me, the debate is more: Would you rather have a fly ball pitcher who averages 7 SO/9 or a groundball pitcher who averages 5 SO/9? Roy Halladay gets a high percentage of groundball outs, but he also registers a fair number of strikeouts.
In the end, it would be interesting to study pitchers' health records and see if Bill's claim that groundball guys get hurt more often is accurate. Or maybe we're just back to that old adage: Always bet on a strikeout pitcher.