Hauser (back) has been ruled out for Monday's game against Milwaukee, Marc D'Amico of the Celtics' official site reports.
Hauser will miss a third straight game due to lower back pain, and his next chance at playing will be Wednesday against the Pacers. Xavier Tillman, Payton Pritchard and Luke Kornet were the only reserves to see playing time against the Pistons on Saturday, though with Hauser out again, Jordan Walsh or Jaden Springer could get a brief look Monday.