Mbah a Moute underwent an MRI on Wednesday morning in Houston and a precise timetable for his return is unclear, the source said. Houston (65-16) will be the top seed in the West playoffs.
He suffered the injury while dunking in the second quarter. He held his shoulder in pain and immediately left the game with 6:46 remaining in the first half.
A 10-year veteran, Mbah a Moute missed 15 games after dislocating his right shoulder in mid-December.
Mbah a Moute entered Tuesday averaging 7.5 points and 25.6 minutes per game this season. He had two points and two rebounds when he departed with the injury.
ESPN's Ohm Youngmisuk contributed to this report.