Boston Celtics president of basketball operations Danny Ainge denied the Brooklyn Nets permission to speak to Doc Rivers about their vacant coaching position, team and league sources confirmed to ESPNBoston.com.

Rivers has three years and $21 million remaining on his contract. The Nets did not retain interim coach P.J. Carlesimo after getting knocked out of the playoffs earlier this month.

Reached late Thursday, Ainge refused to comment on the Nets' interest in Rivers and reiterated that he expects him back on the Celtics' bench next season.

"Doc has told me he's coming back," Ainge said bluntly. "I talk to him almost every day about our team and what we are going to do moving forward."

The Celtics' unwillingness to allow a competing team to talk to Rivers suggests they expect him to honor the extension he signed on May 11, 2011, which made him among the highest-paid coaches in professional sports and one of the top two in the NBA along with the Spurs' Gregg Popovich. When Rivers signed that deal, he was asked about the lean years that inevitably would surface as Paul Pierce, Kevin Garnett and Ray Allen grew older, moved on or retired.

"Well, I don't think anyone is looking forward to [rebuilding]," Rivers said, "but I'm willing to do that. I've had a group that has been very loyal to me, and I think it would have been very easy to just run and go somewhere else and chase something else. ... I just don't think that's the right thing to do. Coaches talk about loyalty and team, and I just thought it was time to show it."