Harper hurt his hand with a head-first 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 proscribed treatment is ice.
"Hopefully 15 days go by and I can get back out there," Harper said. "We'll see how I feel in 15."
Harper joins starting catcher Wilson Ramos and starting third baseman Ryan Zimmerman on the disabled list, both with hand injuries. Ramos, hurt on Opening Day, had surgery on his left hand. Zimmerman broke his right thumb, also sliding into a bag, on April 12.
"We've got a lot of off days in the next 15, so that's huge," Harper said.
Harper went 2 for 2 and had a career-high four RBIs on Friday night, giving him nine for the season as he lifted his batting average to .289. He has only one home run in 83 at-bats.
"It's frustrating," Harper said. "I want to be out there and be able to help my team win every single day."
Steven Souza Jr. was recalled from Triple-A Syracuse to replace him on the roster but was not in the lineup Sunday.