Emilio Bonifacio sent a liner up the middle that hit just above Coffey's right elbow after the reliever entered for starter Jason Marquis in the seventh with one on and two out. X-rays were negative, but Coffey had substantial swelling.
"Obviously it's a little sore. I already did about three rounds of ice and treatment on it, the key now is just to knock the swelling down," Coffey said. "I'm going to go home and ice it continually all night, put a compression sleeve on and try to flush the swelling out. Hopefully it's just a day."
Coffey said his first concern was to find the ball, but when it bounced between shortstop Alex Cora and third baseman Jerry Hairston Jr., the reliever headed toward the dugout, pointing at his elbow.
Bonifacio reached first base safely and Chris Coghlan, who had hit an RBI single, advanced to second. Manager Jim Riggleman and assistant athletic trainer Michael McGowan met Coffey by the first-base line before he left the game.
Tyler Clippard, who was already warming in the bullpen, entered for Coffey and got Hanley Ramirez to fly out to center field to end the inning.
"It's even worse I didn't get the job done -- get the out and get out of the inning," Coffey said. "But I'm going to charge in [from the bullpen] the next time. Hopefully I'll be ready to go in a day or two."
With Coffey's status uncertain over the next few days, the emergence of rookie Cole Kimball can help ease Riggleman's concerns.
The right-hander appeared in both games since his promotion from Triple-A Syracuse, pitching two scoreless innings and ending Sunday's 8-4 victory over the Marlins with a strikeout.
"Him and Coffey are both power pitchers and [their stepping up] would be huge for us," Riggleman said. "With what happened to Todd today, we'll see how quickly we can get him back. Both of those guys have to carry some of the load there and I'm sure they will."
Steven Miller is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.