Garnett has been out for two weeks since straining a stomach muscle against the Timberwolves in Boston. The Celtics went 4-2 in their first six games without him, and they still have the best record in the NBA.
Garnett was the leading vote-getter for the Feb. 17 All-Star game in New Orleans. But Rivers said before Garnett did not dress for Sunday's game against the San Antonio Spurs that he would probably not play Tuesday or Wednesday, in Boston's last two games before the break.
"We haven't talked about the All-Star Game at all," Rivers said. "We're trying to get games played. We'll come across that. I think we have to let the league know pretty soon anyway."
Rivers, who will coach the East in the game, said he hoped Ray Allen would be considered as Garnett's replacement.
"He should be (an All-Star) anyway. I wouldn't be surprised if it wasn't Ray they use," Rivers said. "It would be nice to have Ray on. I would take Ray."