Over the past several years, the Yankees have had a spring training competition to determine who the fifth starter in the rotation should be. In 2014, it was between David Phelps, Adam Warren, Vidal Nuno and Michael Pineda, with Pineda winning the spot. Last year, Esmil Rogers, Chase Whitley, Adam Warren and Chris Capuano faced off, with Warren ultimately staying in the rotation until the end of June.
This year looks to be no different, as Brian Cashman has made a point of saying that the Yankees have "six starters for five spots." Assuming that Masahiro Tanaka, Nathan Eovaldi, Pineda and Luis Severino all stay healthy, their rotation spots appear to be locked in. That means that CC Sabathia, Ivan Nova, and possibly Bryan Mitchell will be competing for the fifth spot. The loser(s) of the competition will presumably work as long relievers out of the bullpen. Regardless of what the Yankees say, Sabathia will almost certainly start the season in the rotation.
It is no secret that Sabathia had a rough 2015 season, pitching to a 4.73 ERA and 4.68 FIP while giving up a whopping 28 home runs. It was by far the worst season of his career, if you exclude the 46 innings he pitched in 2014. However, Sabathia seemed to turn the corner in September after he switched to a different knee brace. During September and October, Sabathia posted a 2.17 ERA and opponents hit just .222 against him. Whether he can replicate his performance down the stretch remains to be seen, but there is the hope that the new knee brace will help.
Some Yankee fans clamored for Sabathia to move to the bullpen last year, but that would not necessarily improve the team. One argument in favor of moving Sabathia to the bullpen is that he fares better during his first time through the lineup. Opponents hit .267 with an OPS of .726 during the first three innings against Sabathia last year. Those numbers jumped to .288 and .792, respectively, during innings four through six.
Although it is possible that Sabathia would have better results in the bullpen, pitching out of the 'pen might be too taxing on his body. When Adam Warren and Esmil Rogers worked as long relievers last year, they sometimes made appearances as frequently as every third day. Not to mention the times when they warmed up and did not enter the game. If anything, Sabathia would likely require more rest to prevent his degenerative knee condition from flaring up.
Another argument in favor of moving Sabathia to the bullpen is that he is still very effective against left-handed batters. While it's true that lefties hit just .186/.235/.283 against Sabathia last year, the Yankees' bullpen already has a plethora of lefty pitchers. Aside from Aroldis Chapman and Andrew Miller, fellow lefties Chasen Shreve, Jacob Lindgren and James Pazos could all end up in the Yankees' bullpen. Removing Sabathia from the rotation and replacing him with Nova or Mitchell would also make the Yankees' rotation entirely right-handed.
Frankly, it's difficult to imagine the Yankees paying Sabathia $25 million to pitch out of bullpen. In the past, the Yankees have never really acted like a move to the bullpen was possible, even when he was struggling last season. Things might be different if the other rotation options were better, or if the Yankees had gone out and grabbed a starting pitcher over the offseason.
However, Mitchell is lacking experience and has been underwhelming during his short stint in the big leagues. Additionally, Nova was so bad last year that they actually pulled him out of the rotation down the stretch. Barring any injuries, expect to see Sabathia in the rotation come April.