Barea did not play in the second half because of the injury, the same one that had limited him in recent weeks.
"I'm very, very concerned," Mavs coach Rick Carlisle said. "I think something happened. I don't think it's just that it was a little tight. I'm afraid something happened."
Barea originally injured the groin April 8 and missed two of the Mavs' last three regular-season games. He had led the team in scoring and assists the previous five games, all wins, starring during the streak that was critical to the Mavs making the playoffs.
Barea played 16 minutes Saturday night, scoring 3 points on 1-of-6 shooting. He also had 3 assists and 2 turnovers.
Dallas forward/center David Lee did not play in Game 1 and is doubtful for Game 2 because of a partially torn plantar fascia in his right foot.