Bill Belichick

New England Patriots head coach Bill Belichick takes questions from members of the media during a news conference before a scheduled NFL football practice, Thursday, Jan. 12, 2017, in Foxborough, Mass. (AP Photo/Steven Senne)

(Steven Senne)

Former Boston Celtics coach Doc Rivers has seen New England Patriots coach Bill Belichick's greatness first-hand. He had just started coaching the Celtics in 2004, when he had the chance to see Belichick win his third Super Bowl in four years over the Philadelphia Eagles.

Apparently, Belichick's greatness has left an impression on Rivers, who now coaches the Los Angeles Clippers. Rivers is so impressed with Belichick, that he considers him the best ever.

"I think he is the greatest coach of all time," Rivers said. "In any sport."

.@DocRivers: "I think he's the greatest coach of all-time. In any sport."



Doc, Joe Torre & Coach K talk BB: https://t.co/cDnpLa9sI2 — New England Patriots (@Patriots) January 14, 2017

Rivers was not alone with his praise of Belichick. Former New York Yankees manager Joe Torre and Duke basketball coach Mike Krzyzewski both added their own high praise of the Patriots' coach.

"Bill Belichick I think stands alone as far as greatness," Torre said.

"He is right there with any coach of any sport," Krzyewski said.

Rivers pointed out a specific example of how good Belichick's culture in New England was, noting that Tom Brady was in the front row transcribing everything Rivers said during one of Rivers' visits with the team. Rivers said it was surprising to see someone of Brady's stature taking what he had to say so seriously.

"It trickles down because if you can coach your players and then they can coach either, and if they buy into the coach, then they can police each other," Rivers said.

Rivers also detailed one time when Belichick visited the Celtics locker room -- during the 2007-08 season when the Celtics won the NBA championship.

"He walked in and he stared at everybody and he was just circling around, and he just said, 'You're going to have to kick their asses,' Rivers said. "And then he looked around, and then he left. And the room went crazy."

Watch the full video above to see what else those three great coaches had to say about Belichick.