Wakefield’s Curious Platoon Split

It looks like most of my fellow writers are more sensible than I, and have moved on from constant attention to the two-week-old Fangraphs’ splits. But I cannot help myself: as a pitchf/x-er I have a fondness for Tim Wakefield and I had always remembered hearing that the knuckleball does not have a platoon split. So it was something I had to check out.

Since 2002 Wake has posted an xFIP of 4.79 against LHBs and an xFIP of 4.73 against RHBs — not much of a split. His FIP actually shows a reverse split: 4.38 against LHBs and 4.73 against RHBs. The interesting aspect is that the components show rather large — but complementary — splits.

Looking just at strikeout and walks Wakefield does much better against righties, with 6.56 K/9, 2.78 BB/9 against RHBs and 5.52 K/9, 3.34 BB/9 against LHBs. That would portend an big split. But once the ball is in play the story changes. Righties have a BABIP of .286, with 38% GB and 10.5% HR/FB. Lefties a .264 BABIP, with 42% GB and 8% HR/FB. So lefties are hitting a lower BABIP; more ground balls, so fewer flies; and a lower percentage of those flies make it over the fence. In every way lefties make poorer contact against Wakefield.

I thought that maybe this had to do with Wakefield throwing his pitches in different percentages to RHBs and LHBs. But his numbers a very similar, against both about 85% knucklers,10% fastballs and 5% curves.

So the difference must be in how LHBs and RHBs deal with his knuckleball, and the per-pitch numbers bear this out. Righties whiff on his knuckler more often (20% versus 16%) and swing at more of them out of the zone (27% versus 25%), but when they hit it they make much better contact (.512 slugging on contact versus .435). I don’t know whether this is a difference in approach — righties go up there looking to knock one out of the park while lefties just look to make contact, but I don’t know why that would be — or whether it has to do with how lefties versus righties pick up as it is delivered or what is causing this difference. Anyway it is one more in a long list of wonderful mysteries of the knuckle ball.

Put it all together and Wakefield probably has a slight reverse split. His FIP, which would credit the difference in HR/FB as real while xFIP would ignore the difference, is better against lefties. And that does not credit him for his very low BABIP against LHBs, which after so many batters faced is probably a real difference and makes his performance agianst LHBs even better than his FIP would suggest.

But anyway you look at it the platoon split is pretty small. All else equal if you have two guys and one spot in the rotation and one spot in the pen you would give the rotation spot to the guy with the smaller platoon split — thus opposing managers could not take advantage of it in lineup creation and you could leverage the bigger split of the guy in the bullpen. So that is one argument for putting Wakefield in the rotation. But all else is not equal and, even accounting for Wake’s splitless-ness, there are probably five better starters than Wakefield on Boston’s depth chart. Anyway the point will probably be moot, as there is little chance all six pitchers are healthy at the same time and Wake will get his share of starts and we shall all rejoice.