"I haven't gotten a prediction, but I definitely think he's out this week," Karl said before the Nuggets' game against the Boston Celtics on Monday night.

If that timetable proves correct, Nene will miss four games and be back when the Nuggets travel to Detroit on March 3.

Nene was injured in the final minute of Denver's 120-117 loss at Milwaukee on Sunday night when he banged knees with Bucks forward Richard Jefferson.

The Nuggets were worried at first because Nene, who tore the ACL in the same knee in 2005, was in a lot of pain afterward and limped out of the Bradley Center on crutches.

The sixth-year Brazilian big man is having a breakout season and has earned strong consideration for the NBA's most improved player award. He ranks first in the league with a .609 field goal percentage and is averaging career-bests with 14.9 points and 7.9 rebounds per game.

His play in the paint is a big reason the resurgent Nuggets are leading the Northwest Division.

Nuggets forward Kenyon Martin, who missed the past 1 1/2 games with back spasms, returned to action against the Celtics.