WALTHAM, Mass. — The Boston Celtics signed Stephon Marbury today, bringing the former New York Knicks headache aboard in their attempt to repeat as NBA champions.

Marbury cleared waivers on Friday morning, reported to the Celtics for a physical and was expected to be in uniform on Friday night for Boston's game against the Indiana Pacers.

"We are very excited to have a player of Stephon's caliber joining our team," Celtics general manager Danny Ainge said. "Our entire organization is confident in the belief that Stephon can play an important role in helping us to win another championship."

Marbury, a former All-Star guard who alienated Knicks management, teammates and fans, was waived on Tuesday after he agreed to a buyout of his $20.8 million contract. The Celtics were expected to offer him a pro-rated share of the veteran's $1.3 million minimum.

Marbury, who turned 32 last week, hasn't played a regular-season game in more than a year.

He arrived at the team's practice facility in Waltham just before noon, about 90 minutes after clearing waivers. He could be seen from the public area of the workout facility wearing a white, long-sleeved T-shirt and sweat pants, jumping up and down as he took the practice court, smiling and chest-bumping with several people wearing Celtics gear.

After few minutes, the automatic shades were lowered.

Marbury will back up Rajon Rondo at point guard, a role Sam Cassell served when the Celtics won their 17th NBA title last season. Eddie House, who is more of a shooter, has been forced into the role this year; Cassell did not play in a game for Boston this year before he was traded to the Sacramento Kings and released last week.

Marbury took a long leave of absence from the Knicks when his father died in December 2007, then had season-ending ankle surgery and has not played since Jan. 11, 2008.

He returned to the Knicks in training camp, but when the sides tried to negotiate a buyout early in the season, Marbury at first refused to surrender any more than $1 million of his $20.8 million salary and the team told him to stay home until it could be completed.

Marbury was the center of controversy during his five years in New York, feuding with coaches and skipping games.