Flagg exited to the locker room in the second quarter of Friday's game against Indiana due to an apparent left shoulder injury, Grant Afseth of DallasHoopsJournal.com reports.
Flagg was hit while he was in the air and landed on his shoulder. He headed to the locker room shortly before halftime and can be considered questionable to return in the second half until the Mavericks provide an update on his status.