"It's just something where he needed to take a game," Mavericks coach Rick Carlisle said pregame, adding that Doncic's back had been bothering him for 2½ weeks.
Doncic is still expected to play in Sunday's All-Star Game in Atlanta, Carlisle said.
Doncic was selected as an All-Star starter for the second consecutive season. He is averaging 28.6 points, 8.4 rebounds and 9.0 assists per game.
Entering Wednesday, Doncic had missed only one game this season for the 18-16 Mavs, who have now won nine of their past 11 games to climb above .500.