From Tyler Kepner of The New York Times:

There is some fear that Rivera could need arthroscopic surgery, although the procedure would be minor and would not be expected to affect him next spring.

“The only way that would happen is if tests indicate that should happen,” General Manager Brian Cashman said of the surgery. “I can’t say at this point.”

Cashman said Rivera expressed a small level of discomfort to team trainers but would not have been sent home if the Yankees were still in the race. He said he expected Rivera to rejoin the team in Boston on Friday and be available to pitch this weekend.

Via Peter Abraham.