"I'm concerned, not as far as him getting tired," Rivers said. "But him to save himself on the floor."
According to Comcast SportsNet New England's A. Sherrod Blakely, Rondo is averaging a team-high 41.5 minutes per game, the second-highest total in the NBA.
Unfortunately, Rondo's increased minutes and production -- he's averaging 15.3 points and a team-high 12 assists per game -- hasn't helped the Celtics (1-2) in the win-loss column.
And because Rondo's increased playing time hasn't led to a better record, Rivers says he's going to need to start looking for a balance between keeping his best player on the floor without over using him.
"We'll figure it out, where he can play his minutes at full pace instead of knowing he's going to be on the floor too long and start pacing himself," Rivers said. "We need him to be a fast, quick, aggressive player."
The Celtics return to action Wednesday when they host the Washington Wizards at the TD Garden (7:30 p.m. ET). On Saturday, Boston defeated Washington, 89-86, behind Rondo's 12 points and 12 assists.