The Yankees placed Cousins (pectoral) on the 15-day injured list Sunday, retroactive to Sept. 20.
There was initial optimism that Cousins would avoid the IL after he left Thursday's game with pectoral tightness, but his regular season is officially over after he was diagnosed with a right pec strain. Cousins has pitched well this season with a 2.37 ERA and 1.05 WHIP in 38 innings, and the Yankees are likely holding out hope that he can be an option in the postseason.