Also Sunday, third baseman Ryan Zimmerman was awaiting the results of an MRI on his right shoulder.
Zimmerman committed his second throwing error of the season Saturday night, leading to two unearned runs in a loss to the Atlanta Braves. He's experienced throwing problems since having shoulder surgery after the 2012 season.
Zimmerman wasn't in the lineup for Sunday's series finale. Also sitting out was slugger Bryce Harper, who is hitting .143.
Hairston says he was hurt while swinging during an at-bat against the New York Mets on Thursday.
Replacing Hairston on the roster is first baseman-outfielder Tyler Moore, who was recalled from Triple-A Syracuse.