Harper hurt his hand with a headfirst slide into third base Friday night after hitting a third-inning, bases-loaded triple in Washington's 11-1 victory. He stayed in the game for an inning before he was replaced.
"It's part of baseball. You slide into the bag and sometimes you get your fingers," Harper said. "It's a bummer, but hopefully I'll be back soon."
Harper will fly to Cleveland on Monday to see prominent hand specialist Thomas Graham for a second opinion. For now, his prescribed treatment is ice.
The Baltimore Orioles put first baseman Chris Davis on the 15-day DL because of a strained left oblique.
The move is retroactive to Saturday. Davis left Friday night's game against Kansas City after four innings and has not played since.
Baltimore did not make a move Sunday to fill the roster spot. The Orioles are off Monday, and Manager