Manager Dusty Baker told reporters that Bregman will be evaluated further and could be out for "a while."
"The way he walked into the clubhouse, it wasn't a good sign," Baker said. "You hate to lose him for any amount of time."
Bregman was injured in the first inning while running to first base when he grounded into a double play. He pulled up a few steps before first base and hobbled off the field after the play before heading to the clubhouse.
He was replaced by Robel García to start the second inning.
Bregman is hitting .275 with seven homers and 34 RBIs this season.
Information from The Associated Press was used in this report.