Earlier in the season the Yankees were just trying to figure out how to fill a five-pitcher rotation after injuries to Masahiro Tanaka and Chase Whitley left them short on starting pitchers. Now, with Ivan Nova starting his rehab assignment with Single-A Tampa today, they will have a huge decision to make possibly before the month of June ends.
With the way CC Sabathia has pitched in his last two starts, there is no way he will be removed from the rotation. He hasn't been great by any means, but he has been good enough to keep his job. Even if he had continued to pitch horribly the Yankees probably would not have removed him from the rotation, but now he has definitely bought himself some time. I was expecting the worst yesterday with Sabathia facing a mostly right-handed Angels lineup at Yankee Stadium, so his seven strikeouts and one walk performance over six innings was very impressive.
Adam Warren certainly hasn't done anything to be taken out of the rotation and is really forcing the Yankees' hand. You can't just take a pitcher pitching this well out of the mix. Now Warren's FIP is 4.67, his xFIP is 4.53, he has a 5.32 K/9 rate compared to a 3.08 BB/9 rate and his BABIP is a minuscule .246, so there has been some measure of luck with him that is probably due for some correction. However, until that correction comes you can't justify removing Warren from the rotation.
So, a six-man rotation for the Yankees is really starting to make sense. I'm not suggesting it lasts the whole season, but rather just a few weeks so the Yankees can gather more info on these pitchers while keeping Michael Pineda and Tanaka rested.
The Yankees are already giving Pineda some time off to keep his innings down, and keeping Tanaka healthy is probably the key to this season. This is even more important if the Yankees make the playoffs because Pineda and Tanaka will get added innings there. Also, Nova won't be able to throw many pitches or innings right away coming off Tommy John surgery.
Where the six-man rotation would hurt the team is in either losing a fourth player off the bench or a pitcher in the bullpen. Neither Chris Capuano nor Esmil Rogers is needed in the bullpen let alone both of them, so either would be an easy cut. Going to a three-man bench would be really dicey, however, especially with Joe Girardi using his bench more often this season. Chris Young has been replacing Carlos Beltran on defense in every game, Jose Pirela is mashing left-handed pitching, Garrett Jones has gotten hot, and obviously John Ryan Murphy is the backup catcher, so everybody there has an important role.
We're still a few weeks away from the Yankees having to make this decision and hopefully it isn't made for them with an injury. The Mets recently scrapped their six-man rotation idea, but it did not make sense for them to begin with. Dillon Gee isn't a good pitcher, and taking starts away from Matt Harvey, Jacob deGrom and Bartolo Colon to give to him makes no sense. However, with the Yankees trying to protect their aces at the top of their rotation it makes much more sense for them and is something to consider.