Porzingis is questionable for Tuesday's game against the Nets due to a low back contusion, Taylor Snow of the Celtics' official site reports.
Porzingis sustained his back injury in Sunday's game against the Heat but was able to return to the contest. However, it's not yet clear whether he'll be able to suit up Tuesday. Xavier Tillman (knee) has been ruled out for Tuesday's matchup, so Luke Kornet and Al Horford should see additional playing time if Porzingis is unavailable.