Orioles catcher Matt Wieters led off the 12th against Chamberlain with a broken-bat single to left field, with all but the handle of the bat heading back up the middle and caroming off Chamberlain's fully exposed right elbow, which was repaired last June by Tommy John surgery.
X-rays were negative, and the righty reliever was diagnosed with a bruise. He will be re-evaluated on Friday, when he plans to play catch prior to ALDS Game 5, which will pit CC Sabathia against Jason Hammel at 5 p.m. ET on TBS.
"I've kind of been through every situation, but thank God it didn't hit me in the head," Chamberlain said. "I'll take this over it hitting me in the head, that's for sure."
Chamberlain heard the bat break as it made contact with his 93-mph fastball, but he attempted to follow the flight of the ball and noticed that the bat was headed toward him only at the last moment. Chamberlain fell to a knee as Wieters ran to first base, and he then threw a few warmup pitches in an attempt to continue.
Manager Joe Girardi and head athletic trainer Steve Donohue looked on as Chamberlain threw his warmup pitches, and Girardi noticed some early swelling, prompting him to lift Chamberlain in favor of rookie David Phelps with one on and no outs.
"I was just concerned that a little bit of swelling could cause some command issues," Girardi said. "So I made a change."
Phelps escaped the 12th inning but surrendered the decisive run an inning later, while Chamberlain iced his elbow and put a compression pad on it. Chamberlain said there was minimal swelling and no numbness, just a bruise.
The right-hander threw a scoreless 11th inning in his first appearance of the series. He missed most of the season while recovering from elbow surgery and an open dislocation of his right ankle, which he sustained in March while playing with his son on a trampoline.
"I don't know if I would hang out with me very much -- I might need a bubble," Chamberlain said. "But it happens. It's one of those things. You take care of it and get after it tomorrow."
Steven Miller is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.