WASHINGTON (AP) — The Washington Nationals say Bryce Harper has a “significant” bone bruise in his left knee but no ligament damage, and general manager Mike Rizzo is hopeful the star outfielder will be back this season.

Harper injured his knee when he slipped on first base in the first inning of a rain-delayed game against the San Francisco Giants on Saturday night. Rizzo said Sunday that Harper had an MRI afterward that showed no structural damage.

“Although we feel we’ve dodged a bullet a bit here with any long-term ligament and tendon damage, 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.”

Rizzo says there’s no timetable for Harper to return. The team is placing him on the 10-day disabled list and activating outfielder Michael Taylor.

Harper, the 2015 National League MVP, is having another spectacular season for division-leading Washington, hitting .326 with 29 home runs and 87 RBIs.

Rizzo — and anyone watching the play — feared it was a serious, potentially season-ending injury. Harper clutched at his left knee and didn’t put any weight on it as he was helped off the field.

“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.”

Rizzo cautioned that “the bone bruise is real” and that the team has the luxury of being extra cautious because of its 14½-game lead in the NL East. Given injuries to Harper, Stephen Strasburg — who has a rehab assignment Monday — and others, the Nationals’ focus is getting healthy for the playoffs.

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