Was Watching touches on what can only be described as a good problem; what to do with Gary Sheffield. He quotes a Ken Rosenthal article:

Thus, the return of Gary Sheffield would muddle the equation for the Yankees, even if Matsui is cleared to play the outfield coming off his broken left wrist. With Bobby Abreu in right, Sheffield could get at-bats at DH and first base. But the Yankees would suffer defensively if he were in the field.

A Sheffield-Jason Giambi platoon at first is not without appeal -- Giambi is batting only .210 against left-handers. Then again, it's difficult to imagine the Yankees trusting Sheffield at first, a position he has never played, in the post-season.

Melky Cabrera in left makes the Yankees a better team defensively. But why not just platoon Sheffield and Matsui at DH? No matter what lineup you put out there, the Yankees are going to have as their worst OBA Robinson Cano's .363. So you say to Matsui and Sheffield, we don't want to risk the long term health of your wrists by your playing the field. Platooning at DH allows the other to step in when a pinch hitter is needed. And with that kind of offense, why not put a better defensive team on the field?