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For most of the last three months, Doc Rivers has relayed optimistic reports on Shaquille O'Neal's recovery from a "minor" injury to his right calf.

One thing the Boston Celtics coach doesn't need to hear from a trainer: whether O'Neal will be any good once he does return.

"He's still big," Rivers said before practice on Friday. "When he's on the floor, he's seven feet tall — plus — and he weighs what he weighs. Of all the players on the team, he has the easiest task of being who he is. Because that's all he can be."

Rivers said O'Neal would take part in a limited workout on Friday, a day after he ran through some plays and shot baskets while his teammates practiced in earnest for Sunday's opener of the Eastern Conference semifinals against the Heat in Miami. Rivers said he's more confident than ever that O'Neal will play in the series.

"I don't know when," the coach said. "Maybe (Game) 1, maybe 2."

O'Neal was not available for comment at the Celtics' practice facility on Thursday or Friday. General manager Danny Ainge said he hasn't seen O'Neal run, but backup center Glen "Big Baby" Davis said O'Neal "looked good."

"And he says he's OK," Davis said. "I'm looking forward to him being back."

O'Neal signed with the Celtics for the veteran's minimum last summer, saying he joined Boston's Big Three for a chance at another title or two before he ended his Hall of Fame career. He played only 37 games in the regular season, and just 5 minutes, 29 seconds since Feb. 1 because of lingering leg problems that have left him perpetually day-to-day.

An injury that was originally supposed to keep him out for a few games has now cost him 33 of the last 34 games of the regular season and the entire, four-game series against the New York Knicks in the first round of the playoffs. Ainge said the future Hall of Famer has been struggling with his downtime and eager to return.

"I think he was probably discouraged in the New York series. He was really determined to get out on the court," Ainge said Friday. "Sometimes, the body doesn't do what the mind wants. But it definitely wasn't because of a lack of will."

The Heat are expecting O'Neal to bring his 345 pounds — and six fouls — onto the court for what is expected to be a physical series between the teams that, while not exactly rivals, have plenty of history. Twice in the last three years the Celtics knocked LeBron James' Cleveland Cavaliers out of the playoffs; last year, that was one round after Boston sent Miami home.

"We don't know what's going on there. But, obviously, it's a big series for both teams," said Heat center and former O'Neal teammate Zydrunas Ilgauskas. "So, unless it's something healthwise, I would expect him to be there."

And health is the only thing that would keep O'Neal away. The team is being extra careful because O'Neal did return once, on April 3, only to re-injure himself.

He hasn't played since.

"He's a competitor. He wants to be on the floor to really help that team," James said. "We'll see when Sunday gets here and throughout the rest of the series if he's going to be in uniform. But it doesn't change our game plan at all."

When O'Neal returns, Rivers said, he will come off the bench; he wasn't able to guess how many minutes.

Davis said O'Neal will help clog the lane on defense, and bring more playoff experience than the Celtics' other centers. With four All-Stars already in the lineup, Davis said, "we just need a little bit of offense from him."

But the good news is that O'Neal doesn't need to relearn how to be tall and strong.

"He has six fouls. He clogs the paint. He's a big body," Heat star Dwyane Wade said. "Of course, it's a positive for them if he's as full-strength as possible."

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AP Sports Writer Tim Reynolds contributed to this story from Miami.