WALTHAM, Mass. (AP) — Forward Jeff Green had successful surgery Monday at the Cleveland Clinic to repair an aeortic aneurysm, discovered by the Celtics medical staff during a routine entrance physical in December.

Coach Doc Rivers received the news following practice on Monday from team president Danny Ainge.

“Surgery went well,” Rivers said. “They’re saying it went great. Obviously, our thoughts, our prayers and every part of our being is with Jeff right now.”

Green was acquired in a trade with the Oklahoma City Thunder at the trade deadline last season that sent center Kendrick Perkins to the Thunder.

Green figured to be a key player for the Celtics this season, as the first man off the bench.

Also Monday, new Celtics forward Mickael Pietrus guaranteed that he’ll make his Boston debut tonight when the Celtics play host the Dallas Mavericks. Pietrus missed the season’s first two weeks after rehabilitation of arthroscopic right knee surgery.

“Today, I went through my first practice,” Pietrus said. “It feels good to be a Celtic. I had fun.”