Doc Rivers is back on an NBA bench just days after leaving the L.A. Clippers ... agreeing to become the next head coach of the Philadelphia 76ers, according to ESPN's Adrian Wojnarowski.

The longtime L.A. coach mutually parted ways with the Clips earlier this week ... after a disappointing exit from the playoffs.

Rivers addressed the exit in a statement, saying, "While I was able to accomplish most of my goals, I won't be able to see them all through. Though it was a disappointing ending to our season, you are right there and I know what this team is capable of accomplishing with your support."

Rivers made it clear he wasn't ready to hang up his tie just yet ... and while an official announcement has yet to be made, it's only a matter of time.

Rivers -- who has posted a 943-681 record as a head coach -- beat out huge names like Mike D'Antoni and Ty Lue for the gig ... and is taking on a team with a ton of talent.

The Sixers have been hoping to get back into the Finals for years ... and now they got a guy who has won it all.