The return of Boston Celtics star Rajon Rondo from his ACL injury is uncertain.  While the guard is eager to return to the court, he conceded it may not be before winter.  Despite his reputation as a mercurial player, Rondo is becoming "best friends" with new Celtics coach Brad Stevens, NBA.com reports.

Rondo isn't finished rehabbing from his knee surgery.  Just over nine months removed from his ACL tear, Rondo is making progress - he's on the court practicing shooting and ball handling, but is unable to participate in any drills involving contact.

There's no timetable for his return, but Rondo believes he won't be ready until sometime in the winter or, at best, the fall.  His injury typically takes a full year to heal.  Still, even once he is physically cleared to play, Rondo must overcome the mental hurdle of trusting his knee again.

"When I'm mentally ready, I'll play," Rondo said, via NBA.com.  "This injury isn't easy.  It's more mental when you come back, and you get around 10-11 months, it's just feeling confident.

"You need that mental aspect to go up and jump and come down without thinking about your leg again.  ... When I get there, I'll play."

In addition to recovering from ACL surgery, Rondo has a new coach to adjust to.  Rondo has a history of butting heads with his former coach, Doc Rivers.  Yet, according to Rondo, he and Stevens are getting along great.

"Me and Brad have become best friends," Rondo said, via ESPN.  "We talk every day, we laugh and joke, we just had dinner the other night.  I'm going to help him, he's going to help me.  He has my full support and I told him from Day 1 when he came to my [summer] camp [in Louisville in July for their first in-person meeting], I'm 100 percent behind him."

While Paul Pierce and Rivers reportedly didn't want part in the Celtics' rebuild, Rondo is excited about stepping into the role of team leader.

"This is a fresh start for us," Rondo said.  "I'm excited about this fresh start."

The Celtics have said they want Rondo to be a key part of the rebuild.  Entering the final year of his contract, Rondo can cash in next season if he's able to helm the team.