"It stiffened on him in batting practice, the last swing," Mattingly said. "We don't expect it to be anything major."
Enrique Hernandez, who started Thursday night's game at second base, replaced Guerrero in left field, batting sixth. He had two hits and scored a run.
Guerrero was an April sensation with a .423 average, five homers and 13 RBIs, despite having only 26 at-bats in 13 games.
Since then, however, Guerrero is hitting .211 with five home runs and 17 RBIs in 58 games.
Ken Gurnick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.