The Nationals are optimistic that Harper will return at some point this season, general manager Mike Rizzo said Sunday.
"We dodged a bullet here," said Rizzo, adding that it was "pretty remarkable" that Harper avoided a more significant injury.
"The bone bruise is something of significance, and we're going to treat him cautiously and hopefully have him back later on this season," Rizzo said. "We put ourselves in a position that we can treat it cautiously, and we'll continue down that road."
The Nationals placed Harper on the 10-day disabled list and activated outfielder Michael Taylor before Sunday's doubleheader against the Giants. Taylor hasn't played since July 6 because of a right oblique strain.
Harper suffered the injury when he slipped on a wet first base in the first inning of Saturday's 3-1 victory?over the San Francisco Giants. While running out a ground ball to the right side of the infield, Harper avoided contact with first baseman Ryder Jones before his left foot slipped on the base.?Harper's leg buckled, he went airborne and he fell to the ground as his helmet went flying.
"We were all holding our breath last night a little bit and hoping for the best," Rizzo said. "Got a glimmer of hope last night when he was able to walk up the stairs from the dugout to the clubhouse and put some weight on it. Had some optimism."
Saturday's game began just after 10 p.m., following a three-hour rain delay.?It was raining steadily when Harper's injury happened.
Washington's championship hopes hinge largely on Harper's health. The 2015 MVP is having another characteristic season, hitting .326 with 29 home runs and 87 RBIs.
The Nationals entered Sunday with a 14?-game lead in the National League East.
The Associated Press contributed to this report.