Rajon Rondo was having his best season for the struggling Boston Celtics.

He was averaging career highs in points and rebounds. He led the NBA in assists and triple-doubles by big margins. He was voted the starting point guard for the Eastern Conference in next month's All-Star Game.

"He's our guy that's orchestrating everything for us," guard Courtney Lee said. "He's our leader."

Not anymore.

Rondo is out for the season with a torn anterior cruciate ligament in his right knee that requires surgery. So coach Doc Rivers must find a replacement from a group short on point-guard experience amid a widespread feeling the Celtics' already shaky playoff prospects are over.

He doesn't believe it.

"You can write the obituary," Rivers said after Sunday's 100-98, double-overtime win over the Miami Heat. "I'm not. You can go ahead, but I'm not. We won (Sunday) and so the way I look at it is we're going to stay in there."

Lee could fill in at Rondo's position. Or Jason Terry. Or Leandro Barbosa. Or, less likely, the Celtics could sign a free agent or trade for a point guard. Their first practice without Rondo was set for Tuesday.

"When something like this happens, someone will find someone that's already in our locker room that's going to play terrific," Rivers said. "And I have no idea who it is."

Sunday's victory moved the Celtics (21-23) ahead of the Philadelphia 76ers by 2 1/2 games for the eighth and final playoff spot in the East. Their first full game since Rondo was ruled out for the season is on Wednesday night at home against the Sacramento Kings.

Rivers' players needed a break after their second straight double-overtime game and their third game in four days so he gave them Monday off.