After hitting the ground rather hard, Hamilton got up slowly. The Reds announced that Hamilton sprained the third and fourth knuckles on his left hand.
Although he finished the top of the inning, he was lifted for pinch-hitter Chris Heisey to open the bottom of the first.
"He dove for a ball and jammed his fingers, and unfortunately, it was the same hand he had jammed earlier in the year in New York [on April 4]," Reds manager Bryan Price said. "We're optimistic it will only be a day or two. But again, you never know until you see him in a day or two. We won't anticipate him playing [Friday] or at least starting in the outfield. But there are probably some things he can do to help us win a game."
In 27 games, Hamilton is batting .245 with one home run, six RBIs and 11 stolen bases in 16 attempts.
Injuries have plagued the Reds this season, and they've already put 10 players on the disabled list. Earlier in the day, starting pitcher Tony Cingrani went on the DL with left shoulder tendinitis.
Mark Sheldon is a reporter for MLB.com. Read his blog, Mark My Word, and follow him on Twitter @m_sheldon. This story was not subject to the approval of Major League Baseball or its clubs.