The Yankees have a 99.5 percent chance of making the postseason according to Baseball Prospectus's Postseason Odds. They enter Saturday's action with a half-game lead in the AL East and a 8 1/2-game lead on Rays, the second-place team in the Wild Card race, and thus the team closest to bumping them out of a playoff spot. The division title will decide their first-round opponent in the playoffs (as things stand, the division winner would face the Tigers while the Wild Card would face the Rangers) and will determine home-field advantage in a potential ALCS matchup against the Red Sox. Those things aren't completely insignificant, but, really, the Yankees' goals for the remaining 39 games of the regular season should be to evaluate their players for potential inclusion on the playoff roster and to get those players healthy for October.
It was with those goals in mind that I recommended, against my personal preference for smaller rotations, that the Yankees stick with their current six-man rotation until injury or poor performance forces them to drop one of those six starters from that group (indeed, a cut finger has temporarily taken Freddy Garcia out of that sextet, but he's due to return a week from today). The decisions they make about the rotation will impact their decisions about the bullpen, and there's no need to rush into either. Things are a bit more clear-cut when it comes to the rest of the roster. These eight starters, for example, are locks, health permitting:
1B - Mark Teixeira (S)
2B - Robinson Cano (L)
SS - Derek Jeter (R)
3B - Alex Rodriguez (R)
C - Russell Martin (R)
RF - Nick Swisher (S)
CF - Curtis Granderson
LF - Brett Gardner (L)
To them you can add Andruw Jones as the right-handed designated hitter, Francisco Cervelli as the backup catcher, Eduardo Nuñez as the utility infielder, and since the Yankees will need a bench outfielder when Jones is the DH, Chris Dickerson, who should return to the majors when rosters expand on September 1. That's twelve hitters covering everything except a left-handed DH (assuming the Yankees don't plan on starting Dickerson, a player who hasn't been on the 25-man roster since July, in the majority of their payoff games).
The obvious candidates for that lefty DH spot are Eric Chavez and Jorge Posada. The Yankees could certainly get away with carrying both along with 11 pitchers as that would still give them seven men in the bullpen with a four-man playoff rotation. That supports the fact that the key decisions about the playoff roster will come on the pitching side of things, with the team needing not only to trim their six-man rotation down to four, but their current stock of 14 pitchers (13 on the 25-man roster plus Garcia) down to 11.
However, it also points to the fact that the Yankees need to figure out who their starting left-handed DH is. Jones has started the Yankees' last 15 games against a left-handed starting pitcher dating back to June 20, is hitting .278/.381/.536 against lefties on the season, and has hit .349/.481/.674 overall since making a mechanical adjustment coming out of the All-Star break. So, his share of the DH duties seems pretty well set in stone. However, Jones has hit just .152/.263/.242 against righties this season, which includes his strong showing in 11 at-bats against them since the break and has hit just .209/.306/.457 against righties in the three seasons since his career-altering season with the Dodgers.
Chavez offers the flexibility of playing third base to allow Alex Rodriguez to DH, but he has hit just .237/.286/.322 in 15 games (all starts) since returning from a nearly three-month disabled list stay on July 26, including a .229/.288/.333 line against righties. He has also hit for very little power this season with just one home run in 102 plate appearances (just 14 of which have come against lefties) and an isolated power of .098 against a league average of .146. That's nothing new. Chavez has just four home runs in 351 PA over the last four seasons and an isolated power over that span of just .106.
That's an easy bar for Posada to clear, and he does so. His season line of .238/.319/.384, weak as it may be, is clearly better than Chavez's post-DL performance, and Posada's .272/.352/.451 line against righties on the season, which includes all ten of his home runs, is well above the league average slash line of .256/.321/.402.
Based on those numbers, it's almost impossible to argue that Chavez should start at DH against a righty over Posada. Unfortunately, Alex Rodriguez is going to need a fair number of games at DH after he returns, which could be as early as today, and neither Posada nor Jones can play third base. Eduardo Nuñez can, however, and his .266/325/.360 line against righties this season is still better than the post-DL Chavez close to an exact match for Chavez's overall season line against righties (.244/.330/.359), but Chavez breaks that particular tie by being the better, and by far more reliable, fielder. Even if you don't trust stats like Ultimate Zone Rating, which say that Chavez is better, its easy to see that Chavez has played 163 2/3 errorless innings at third base for the Yankees, while Nuñez has made one error for every 39 innings he has spent at the hot corner this season.
Nuñez fielding yips are a legitimate concern. Not so much that I'd leave him off the postseason roster in favor of a gloveman like Ramiro Peña, but enough that I can't see any excuse for giving him a postseason start. Jones is hitting so well that he should force Rodriguez into the field against lefties, and Chavez's glove is enough to give him the edge over Nuñez if the Yankees want to DH Rodriguez against the occasional righty.
Still, there are 39 games left in the season, and the Yankees should have no qualms about letting Jones face righties, giving Chavez enough at-bats to try to find some life in his bat, or letting Nuñez try to increase his comfort level at third base. The only trick is that they also have to find enough time in there for Posada to keep his left-handed swing in order as, right now, the ideal postseason Yankee lineup would have Rodriguez in the field and Jones and Posada platooning at DH.