Betts finished 1 for 5 in his return from the disabled list and was lifted in the bottom of the 11th.
Betts had been sidelined since May 27 with an abdominal strain. He missed the Red Sox' past 14 games, with the club going 8-6 in that time.
"It was just a matter of letting it kind of heal,'' said Betts, whose return was quicker than many had anticipated. "We'll see how I feel after the game today and go from there.''
Betts, who batted leadoff Monday, leads the majors in batting average (.359), on-base percentage (.437), slugging percentage (.750), and OPS (1.187).
Betts also has 17 home runs and 37 RBIs in 48 games.
Without Betts in the lineup, the Red Sox have averaged 4.5 runs a game, down almost a run from their average with him in the lineup.
"We talked about it yesterday, me and Mook,'' said Red Sox manager Alex Cora. "He feels comfortable that he can compete at this level, the way he is right now. He's healthy and we agreed to it.''
Shortstop Manny Machado was not in the Orioles lineup Monday.