Bagley left the game in the first minute with the injury. He seemed to slip in the lane defending a fast break and went down, immediately grabbing his knee. He was helped off the court, and Detroit soon announced Bagley, who signed a three-year contract with the Pistons this summer, would not return to the game.
Bagley was set to undergo more tests, and the team will know more Wednesday, coach Dwane Casey said.
The Associated Press contributed to this report.