Last year, behind the efforts of Carlos Pena, the Rays managed a measly .683 OPS from their first basemen. Granted, that is not park adjusted. However, adjusting it for the park only bumps it to a .719 OPS. Last season, the AL combined for a .731 OPS. So from an offensive minded position, the Rays received below league average production.
This season, the Rays have handed the first base position to James Loney. When a first baseman is better regarded for his glove than his bat, there is normally an issue. Loney, in his career, has a 103 wRC+; last year, it was 70. First base is a position from which teams expect offensive production, yet the Rays appear to be in line for league average offensive production. Any way in which the Rays can maximize their offensive output from the position, in my opinion, is an option worth exploring. One of these routes is a platoon at first base.
The Oakland Athletics received a .801 OPS from first base last year through effective platoons. For his career, Loney possesses a 111 wRC+ against RHP while only a 77 wRC+ against LHP. According to Whelk's regressed splits tool (bookmark it if you have not already), Loney has a regressed split of .13419. For comparison's sake, Joyce has a regressed split of .18896.
Bill James projects Loney to have a .319 wOBA this year. Plugging that into Whelk's tool, we can see that Loney should be projected to have a .330 wOBA against RHP and a .287 wOBA against LHP, a figure far below average. While a .330 wOBA against right handed pitching is not a gaudy number, it is solid enough when combined with his plus defense. On the other hand, his .287 wOBA puts him in below replacement level range, something the Rays can ill-afford or hide with their solid rather than spectacular offense.
In 2012, 70% of all MLB plate appearances occurred with a right handed pitcher on the mound. James Loney should and will receive most, if not all, of the plate appearance, health permitting. Against the other 30% of pitchers, it makes sense for the Rays to use one of their right handed bats on the bench(such as Ryan Roberts or Sean Rodriguez) to play first base.
Again using the Bill James projections and Whelk's regressed splits tool, we have Sean Rodriguez hitting for a .338 wOBA versus LHP. Ryan Roberts is projected to hit for a .338 wOBA as well. If Loney receives all 70% of the plate appearances against RHP and Roberts/Rodriguez receive all the plate appearances against LHP, we can project the first base position to have a .332 wOBA. That isn't spectacular, but it is definitely an improvement from last year.
How many runs do the Rays add by simply putting Roberts or Rodriguez at first base for the 210 or so plate appearances? My rough calculations have the move improving the Rays by 9.3 runs, or close to a win (lower the figure a tad bit for defense, if you want). In a tough division such as the AL East, one win could be the difference between the AL East title and the wild card, or the wild card and no playoffs.
If platooning at first base can provide the Rays with another win, then it is an option that they must seriously consider.