Manager Joe Girardi said Monday that the procedure will shave down calcification of the A.C. joint on the top of Rivera's shoulder. The surgery hasn't been scheduled, but Girardi said it doesn't appear to be a serious injury and there is no structural damage.
"From what I've learned, he's had it the whole year. Has it progressively got worse over the course of the year? I don't necessarily think so," Girardi said. "I think he just feels more comfortable having it done and then not have to deal with it next year."
Rivera returned to New York last Thursday for an MRI on the shoulder, then rejoined the Yankees in Boston for the last series of their lost season. He pitched 1 1/3 innings in the opener of Sunday's day-night doubleheader to wrap up Mike Mussina's 20th win.
The 38-year-old Rivera was often called upon to pitch more than one inning this season because of the Yankees' struggling bullpen, but Girardi said that wasn't a factor in the sore shoulder. Rivera finished with 39 saves and his 1.40 ERA was his best since 2005.
Girardi said the date for the surgery and where it will be performed should be set later this week
"I think this is what Mo is most comfortable with," Girardi said. "You're not talking about anything structural with the shoulder."