Since Ivan Nova has returned to the Yankees rotation he has been their second best starter. Hiroki Kuroda has been the best, like he has been all season long, with his 1.86 ERA and .631 OPS against since the third week of June. Nova has put up a 2.49 ERA with a .585 OPS, but from there performance falls off a cliff.
For a team that lists starting pitching as a strength, the Yankees have a lot of issues with several of their starters. Phil Hughes has been mediocre all season long with a 4.07 ERA and a .782 OPS against since Nova was put back in the rotation. Andy Pettitte has been bad, pitching to a 5.10 ERA and .817 OPS against in that same time period. He pitched to a 3.83 ERA and .748 OPS against from the beginning of the season until he hit the DL in mid-May. Since returning at the beginning of June, he's pitched to a 4.84 ERA and .772 OPS against and as bad as that is, the Yankees still have someone who is worse.
CC Sabathia has a 6.34 ERA and a .843 OPS against since Nova has returned and, unfortunately, that's not just a case of small sample size. For the season, CC has a 4.65 ERA and 4.13 FIP, which would be the highest ERA and second highest FIP in the rotation. Sabathia hasn't just struggled, but according to his 160 ERA- he's been the worst pitcher in the rotation. Hughes and Pettitte are obviously vying with him for that honor, but the fact that the Yankees ace is in this discussion is somewhat disturbing.
The worst part is that the only person you could possibly entertain the idea of benching CC for is Michael Pineda and right now the Yankees have begun to manage his innings, so it doesn't look very promising for him. He has a 4.22 ERA, but also a 2.83 FIP in 21.1 innings at Triple-A. The only other viable option is David Phelps, but he's the one pitcher that has been worse and he's been out with a forearm injury since the beginning of July. He has a 5.01 ERA, a .760 OPS against, and a 120 ERA- to make him the worst Yankees pitcher of the season. CC Sabathia isn't going anywhere and the worst part is that Andy Pettitte isn't either. Hold onto your butts!