Williams failed to live up to expectations in Atlanta and he was dealt to Sacramento midway through his second season. Williams then was traded to Minnesota for 15 games last season before becoming a free agent.

Looking for a fresh start, Williams decided to bring his game to the Celtics , signing a one-year contract for the veteran's minimum worth $1.3 million.

``The interest has been there for a while now,'' said Williams, who displayed his No. 13 jersey at yesterday's introductory press conference. ``They've had a strong interest going back to my senior year when I was coming out in the draft. Also, with the tradition here and being in an atmosphere like this, versus the teams I've been on in the league, is something different and I think it'll be a good opportunity.''

Williams has averaged 4.7 points and 4.2 rebounds in 14.4 minutes during his three-year career. Celtics general manager Danny Ainge believes Williams can produce if given the opportunity.

``We think that Shelden is a good young player that hasn't really had much of a chance,'' Ainge said. ``He's a real pro. He works extremely hard. He's worked hard this summer. He faced some adversity early in his career and he's responded in the right way by training and working really hard.''

Williams solidifies the frontcourt depth, which was a major issue in last year's postseason after Kevin Garnett and Leon Powe were lost with knee injuries. With a half-dozen capable front-court veterans now at coach Doc Rivers' disposal, Ainge thinks the Celts have the best front line since the Larry Bird, Kevin McHale and Robert Parish days.

Ainge believes the group that will take the court on opening night in Cleveland on Oct. 27 will be better than the team that won the championship two seasons ago.

Such reinforcements were necessary, as most of the top contenders have stocked up this summer.

``I think the Lakers are getting better; I think Cleveland is getting better,'' Ainge said. ``I think we need to be better.''

Almost full

The signing of Williams coupled with the re-signing of Glen Davis, fills 13 of the 15 roster spots for next season. One of the final spots will go to Indiana swingman Marquis Daniels, as Ainge said the Celtics are ``trying to figure out the best way to get him here.''

Barring the late emergence of a third team to facilitate a sign-and-trade deal, Daniels is expected to sign for the $1.9 million biannual exception.

Second-round draft pick Lester Hudson could fill the final spot on the roster, though Ainge is in no rush to make that decision.

``We still have to . . . really decide what we're going to do with that third point guard position, which I'm not feeling great urgency because I think that both Eddie (House) and Marquis can play there,'' Ainge said.

- danduggan@bostonherald.com