BOSTON – The Celtics have reloaded this year, and are looking for one more piece of the puzzle to round out their championship-caliber team.

The re-signing of power forward Glen Davis and the inking of forward Shelden Williams earlier this week leave the Celtics with just two open roster spaces left.

One of the remaining spots will go to Indiana swingman Marquis Daniels for the $1.9-million biannual exception, unless a sign-and-trade deal can be made. The other is expected to be filled by a point guard to back up Rajon Rondo now that the Celtics have six reliable frontcourt players in Kevin Garnett, Kendrick Perkins, Rasheed Wallace, Davis, Brian Scalabrine and Williams.

“We feel like we have one of the best frontcourts in all of basketball,” Celtics director of basketball operations Danny Ainge said Monday in a news conference to introduce Williams and reintroduce Davis. “We have a great deal of depth.”

In fact, Ainge said the frontcourt the Celtics will field this season could be the best in team history.

“It’s the best frontcourt that we’ve had maybe ever in this franchise – since [Larry] Bird, [Kevin] McHale and [Robert] Parish probably. … Since that era, it’s the best frontcourt we’ve had,” Ainge said. “We think we have good depth and with Scalabrine and Shelden and Glen Davis playing behind the three guys, we have rebounding and we have defense. Big Baby is a very versatile player. Rasheed spreads the floor and we obviously know about Perk and KG. They’ve done a great job for us the last few years.”

Ainge said it is not set in stone that the remaining roster spot will go to a point guard, even though the Celtics only have one pure point guard on the team in Rondo.

“I’m not feeling a great urgency, because I think that both Eddie [House] and Marquis can play there, and even Tony [Allen],” Ainge said. “We won a game [in December 2007] by 20 points against the Lakers with Tony starting at point guard, so it’s not an urgent thing that we are trying to do right now.”

As for Davis, the 23-year-old rising star said he is glad to be back with Boston.

“The Celtics organization is a great thing to be a part of,” Davis said after signing a two-year deal reportedly worth $6.3 million. “Just to be here and be amongst all these great players and be around that winning feeling, you gotta love it. I’m just glad everything is done and we’re finished and we can concentrate on winning basketball games.”

With a healthy Garnett returning and Wallace on the team, Davis’ role might be diminished, but he doesn’t feel that way, especially now that Leon Powe will be playing in Cleveland next year.

“I feel like my role hasn’t changed a lot,” Davis said. “I feel like I just have to be ready to go out there and play. My role is to do whatever I have to do, and I’m going to do it. That’s the kind of attitude you have to have in order to be on a team like this. You have to have that attitude that you are going to go out there and do whatever it takes whenever you get an opportunity to do it.

“That’s just my mental thought process right now – just to make sure that I’m there for my teammates, being in shape and whenever the opportunity comes to play, go out there and deliver.”

Davis averaged 7.0 points and 4.0 rebounds in 21.5 minutes per game. His stats skyrocketed when Garnett went down with a knee injury in the second half of the season, rising from 4.8 points and 3.5 rebounds before the All-Star break to 12.0 points and 5.1 rebounds after it.

In the playoffs, Davis helped the Celtics reach the Eastern Conference semifinals by averaging a career-high 15.8 points and 5.6 rebounds.

Davis feels like he has something to prove this season, and he plans on doing that by making the most of his opportunities, even if they are limited because of how deep Boston’s frontcourt is.

“You have to have a chip on your shoulder a little bit,” Davis said. “You have to have that attitude as far as to prove something to those out there, but everybody knows what I can do in this game and with the right mental approach I feel like I can still help and do a lot of things for the team.”

roblee@projo.com