Celtics center Kendrick Perkins had arthroscopic surgery on his left shoulder Tuesday and is expected to be ready for the start of next season.

Perkins was hurt last week while working out at the team's practice facility in Waltham. He dislocated the same shoulder late in practice Feb. 8 and sat out 13 games before returning March 12.

"We fully expect him back for the start of the season," although he may not be ready when training camp begins about a month earlier in early October, said Jeff Twiss, the Celtics' vice president of media services and alumni relations. "The surgery is more just to tighten the capsule around the (shoulder) joint."

The majority of the Boston beat writers believe the Celtics should trade their draft pick, situated seventh overall, for a veteran presence.

According to Peter May, Danny Ainge says he is exploring just this, May stating ''this team already is young enough, and another veteran would be a big help''.

Bob Ryan of the Boston Globe, the only writer who actually suggests taking a player, would like the Celtics to try to land Connecticut point guard Marcus Williams, if of course he is still on the board when it is the Celtics turn to pick.

Celtics Vice President of Media Relations Jeff Twiss confirmed Friday morning that Kendrick Perkins suffered a shoulder injury during offseason workouts in Waltham on Thursday.

Twiss said that Perkins will be observed by doctors "in the near future" for further diagnosis. There is no definitive word at this time on the nature of the injury, or any timetable on a return.

Perkins had just returned to Waltham to begin offseason workouts this week. Celtics.com will have more information as it becomes available.

Perkins also suffered a shoulder dislocation last season at practice on February 8.

Paul Pierce had planned on having surgery to alleviate his left elbow bursitis, but it managed to heal on its own because of rest.  

?The doctors just didn?t feel like he needed it,? Celtics director of basketball operations Danny Ainge said. ?It was iffy whether he would have surgery, but we were kind of planning on it. Then his elbow just started getting better, and he hasn?t had any problems.

?They drained it during the season and they haven?t drained it since. It?s just gotten better. He had fluid there because he kept banging on it, but once he rested it it?s been fine, so there?s no need to do surgery. I don?t think surgery is ever good. You know, they say minor surgery is what they do on someone else.?

For teams that didn't qualify for the playoffs, like the Boston Celtics, the NBA Draft Lottery represents a chance for an instant reversal of fortune, but Danny Ainge isn't expecting a franchise player, even if the club managed to win the lottery.

``It's not a weak draft," said Ainge. ``It's just weak at the top. In a year where you have LeBron James, Carmelo Anthony, and Dwyane Wade, there isn't that. But from that point on, that's where our draft is. Although there's not as much separation as in most years, I think it's still an advantage to be picking who you want and not be picking who's left over."

Citing personal reasons and poor timing, Jim O'Brien yesterday declined the Celtics' offer of an assistant coaching position, the Boston Globe is reporting.

O'Brien said his decision ''had nothing to do with the Celtics," praising the organization, executives Danny Ainge and Leo Papile, and coach Doc Rivers for their professionalism.

''They were great to me," said O'Brien. ''I'm flattered they had the interest that they had.

''It really is about me and a personal thing with me. The timing is not great for me to make the commitment that I would have to make to do that job properly. It's almost as simple as that.

''I live in Boston. I like the Celtics. I hope they do very, very well. I'm always pulling for them. [The decision] has all to do with where I'm at now."

League sources said yesterday that the Celtics have offered an assistant coaching position to former Boston College head coach Jim O'Brien.

He would be replacing Paul Pressey and Jim Brewer.

According to the Miami Herald, Celtics coach Doc Rivers has jumped to the defense of former Celtic Antoine Walker, saying he didn't deserve the ''freaking heat'' he got from Heat fans earlier in the season.

''When he came here, he knew there would be an adjustment,'' said Rivers, who coached Walker in Boston. ``He didn't do it well early, and I thought people thought that meant he wasn't trying to do it. I always thought he was trying to do the right stuff. It just wasn't working.

``He got so much freaking heat, I was amazed by the criticism he got for trying to fit in, because he didn't fit in the way people wanted. He was unfairly criticized. . . . It's really tough for a guy like Antoine to go from being a guy with the ball in his hand a lot to being a catch-and-shoot [guy]. That's a big role change. I don't think he's gotten comfortable with it until right now, and now you can see it. . . . I felt you had to put the ball in his hands for our team to be effective.''

The Boston Celtics became the final NBA club to add a dance team on Friday when they announced that they would have one for the 2006-2007 season.

According to Rich Gotham, the team's executive vice president of sales and marketing, ''The Celtics Dancers will contribute to the exciting in-game experience for our fans."

A team source said Thursday that the contracts of Boston assistant coaches Jim Brewer and Paul Pressey will not be renewed for next season.

Brewer and Pressey often times worked with players individually or in small groups and were seated behind the bench during games.