"My understanding is that we don't expect it to be serious," coach Rick Carlisle said. "He'll probably be listed as day to day."
The Mavs don't play again until the Memphis Grizzlies visit Wednesday.
Marion injured the muscle while spinning for a layup in the first quarter. He came back into the game but clutched his side after missing a breakaway layup in the second quarter.
Moments later, Marion left the court with Mavs assistant athletic trainer Dionne Calhoun.
The 31-year-old Marion, the Mavs' best defender, has dealt with calf, ankle, groin and back injuries this season but has missed only four games.