On Monday, the Los Angeles Dodgers agreed to sign Marcus Thames to a one-year contract, and followed that up Tuesday by giving Gabe Kapler a minor league deal with an invitation to spring training. By signing two right-handed-hitting outfielders in the span of two days, the Dodgers have made their intentions for 2011 known loud and clear -- they're going to platoon.
General manager Ned Colletti told ESPNLA's Tony Jackson that Thames was signed because they "really needed him against left-handed pitching." The other candidates for playing time in left field are Jay Gibbons, Tony Gwynn Jr. and Xavier Paul, all of whom hit from the left side. By adding Thames, Colletti has created an opportunity for his team to run a platoon in left field, getting the left-right advantage on the starting pitcher in most games.
However, while platooning can be an effective way to get value from players with limited skills, the upside of a job share is often overstated. Too often, the focus is placed only on how each batter does against opposite-handed pitchers; you'll even frequently see people add these lines together to claim that the platoon is going to produce at a rate equal to one legitimately good hitter.
Since 2002, Gibbons has hit .263/.322/.465 against right-handed pitching, good for a 107 wRC+ (meaning he's been 7 percent better than average against RHPs). Against lefties, Thames has hit .264/.333/.505, good for a 119 wRC+. If you combine those lines (giving Gibbons the majority of the playing time, since the left-handed portion of the platoon gets more at-bats), the result is a 110 wRC+, which is essentially equal to the career production of Vernon Wells. That's not bad for just a few million bucks, right?
The problem is that it rarely actually works out this way.