The very good Another Cubs Blog did a post recently on projecting player’s platoon splits, and he was kind enough to include a spreadsheet that one can use to calculate them for any player. Here’s how it works (originally from the process outlined in The Book):
“1. First you figure out the player’s career split percentage. To do this, you need their career wOBA, career wOBA vs RHP, and career wOBA vs LHP. Figure out how much better (or worse) each of these are than their career number…
2. Next, you regress this split percentage against the average. We use percentages because better hitters tend to have bigger splits. We also only use the number of PAs against LHP for this, since batters tend to see less of those pitchers than RHP, so we use this as the ‘baseline’ of how much info we have about the players splits. For right-handed batters, we regress against 2200 PAs of 6.1% split (for lefties it’s 1000 PAs of a 8.6% split)…
3. Next we need to figure out how we ‘spread’ this new regressed split percentage against the player’s projected wOBA for the following year. To do this, we look at the player’s career distribution of PAs, and use this as a weighting to ensure that the projected overall wOBA is obtained.”
Working out an example: Nick Markakis has a career .363 wOBA. He has a career wOBA of .377 against right-handed pitchers (about 4% better than his overall mark), and a wOBA of .327 against left-handed pitchers (about 10% worse than his overall mark) – a difference of 14%. Those wOBAs were compiled in 1,808 and 852 plate appearances, respectively, and once we regress by adding in those league average plate appearances we get splits of about 7% worse than overall versus left-handers and 4% better than overall versus right-handers (a total split of 11%).
Here’s a breakdown for all the O’s batters, with the projected overall wOBA column being the projections I currently have for the players for 2010:
|Projected Overall wOBA||Career Split||Projected Split||Projected wOBA vs. LHP||Projected wOBA vs RHP|
A negative split indicates being better versus the same handed pitcher, so Jones and Reimold have both hit better against right-handers in their career (which we wouldn’t expect to continue). Overall, these O’s batters are a little better against right-handed pitchers (.340 wOBA) than left-handed pitchers (.335 wOBA). There really isn’t anyone that needs to be platooned except for Felix Pie, though he has tended to be spared from left-handers quite often in his career anyway. Nick Markakis has a pretty big platoon split, but he’s a good enough hitter in general that he’s still above average versus south-paws.