— WALTHAM, Mass. — When Shaquille O’Neal was much, much younger and a good deal smaller, too, he chose as a role model one of the most successful big men in NBA history.

“When I came into the league, I wanted to compete with Bill Russell for titles,” O’Neal said Tuesday, with Russell’s 11 championship banners hanging above him at a news conference to mark his signing with the Boston Celtics. “That’s not going to happen, but I’d like to almost get half of what he got.”

With four titles and a Hall of Fame career already on his resume, newly christened “Big Shamrock” signed a two-year deal with the Celtics at veteran’s minimum, forgoing more lucrative offers to join the defending Eastern Conference champions for a run at another championship or two.

A crossover celebrity who has appeared in feature films and his own TV show, O’Neal joked about his new nickname, his fear that his kids will develop a Boston accent and trying to beat new teammate Glen “Big Baby” Davis in a chowder-eating contest.

But he was serious when he talked about his legacy.

“Do I have the same hunger? Yes. If I didn’t, I wouldn’t be here,” O’Neal said. “I don’t like wasting my time. I don’t like wasting anybody’s time. At the end of the day, when I close the book, it’s all about winning.”

The news conference to introduce O’Neal wasn’t the usual type for a backup, 38-year-old center who will be paid about $1.3 million a year. There were a dozen TV cameras, perhaps 50 reporters in all and a couple hundred beaming schoolchildren in the bleachers, taking a break from their basketball camp next door.

Also in the gym: Kevin Garnett, who promised O’Neal he would fly back from Hawaii to be there.

“To me this is a very exclusive event,” said O’Neal, who wore a gray pinstriped suit and a black bow tie. “It’s my last (introductory) press conference. I just wanted to be very, very sharp.”

The crowd was all there to see O’Neal the superstar, the former NBA MVP and four-time champion who is certain to be enshrined in the Hall of Fame down the road in Springfield whenever he decides he’s had enough.

But the O’Neal the Celtics have signed is a much different player than the one who accumulated those credentials.

Now weighing in at 345 pounds — he was 294 at LSU — O’Neal averaged 12 points and 6.7 rebounds for the Cavaliers last season, when he was brought to Cleveland in the hopes that he would be the missing piece that would help LeBron James win his elusive NBA title. He also missed almost two months of the regular season after injuring his thumb against the Celtics.

“I told him there won’t be 30 minutes (for him) on this team; there will be 20-25,” Celtics coach Doc Rivers said. “I asked him if that would be OK, because that’s the only way it’s going to work.”

And it was OK with O’Neal, who hit the free agent market seeking a two-year deal worth a reported $8 million to $10 million a season. The Celtics expressed an interest — though not at that price — and general manager Danny Ainge moved on to pursue other options.

As the summer wore on, though, O’Neal came around. Ainge said O’Neal’s agent called and said, “Shaq would like to play there, and he’s willing to come on your terms.”

“I think Shaq’s a guy who can still make a difference,” Ainge told reporters in a conference call after the news conference. “When he was in his prime, he was considered one of the best who has ever played. Shaq coming to our team right now, our expectations won’t be that. We expect him to contribute to our team and play a role off our bench.”

But that can be a major contribution for a team that is without center Kendrick Perkins for at least half the season while he recovers from the knee injury he sustained during Game 6 of the NBA finals. Backup Rasheed Wallace retired, and the Celtics officially released him on Tuesday.

Boston signed Jermaine O’Neal, another reclamation project, and then added his more illustrious namesake. There won’t be a problem with playing time until Perkins returns.

“Shaq still can do things that no other big man can,” Rivers said. “You need size to win. We think we filled that void pretty well today.”

The Celtics won their NBA-record 17th championship in 2008, then returned to the finals last year before losing to the Los Angeles Lakers in seven games. While the Miami Heat have rebuilt around Dwyane Wade, LeBron James and Chris Bosh, the Celtics have largely brought back the core of last season’s team, re-signing Paul Pierce and Ray Allen to keep them alongside Garnett and point guard Rajon Rondo.

“I realize I only have 730 days left in this game. I just wanted to be with a group of guys that like to win,” O’Neal said. “This was a good team with or without me. I don’t mind playing a role. I know where I am at this point in my career. It’s about coming to a team that is one or two pieces from a championship.”