Shaquille O'Neal out for Game 1

WALTHAM, Mass. -- The Boston Celtics attempted to get Shaquille O'Neal back on the practice court Saturday morning, but his ailing right Achilles tendon and strained right calf would not allow him to go through the activity.

Celtics president of basketball operations Danny Ainge announced soon after that O'Neal would not be ready for Sunday's Game 1 of an Eastern Conference quarterfinals series against the New York Knicks.

"[Shaq's] been making progress and we tried to get him out there to practice today, to simulate a game as much as we could and he's not ready," Ainge said. "We don't know when he'll be ready, and we'll just keep evaluating him day to day. So he won't play in tomorrow's game."

Added team physician Dr. Brian McKeon: "This guy's been working his tail off. He's worked so, so hard, and today we did a mock trial pregame workout and he failed. It didn't work. Just too sore. We'll get back to work tomorrow and keep knowing what we're doing and hopefully we can get him back soon."

O'Neal, who missed a total of 45 games this season, sat out 27 games starting Feb. 1 before returning to the lineup April 3 against the Detroit Pistons. He lasted a mere 5 minutes, 29 seconds before hobbling off with the calf injury and sat out the final six games of the regular season.

According to McKeon, it's the entire "triceps surae complex" that's ailing O'Neal, with both the Achilles and calf still sore. But he stressed that O'Neal has not endured any setbacks.

"He's actually made progression every day," said McKeon. "This is a tough injury. The blood supply in this area is so weak and so poor, it's time. I was telling Danny and the coaches, in the last 20 years this is one area of medicine we've made no progress. Because it's just time. It's just hard to get enough healing potential in that area."

O'Neal passed a similar pregame mock session before returning against Detroit, but couldn't get through the test Saturday. Ainge holds out hope that more time and treatment will allow him to get back on the court.

"I mean, he might come back in three days and feel like it's better, and it's feeling better," said Ainge. "It's not like this magic test. The test is, 'Does it hurt?' You run up and down the court and does it hurt? That's the test, and can you play, and the strength tests. We'll do those every day."

Celtics coach Doc Rivers expressed disappointment for O'Neal given how hard he's worked to be ready for this moment, but admitted his team was prepared without the 39-year-old center.

"The guy's put in a lot of work, he's extremely disappointed that he can't go," said Rivers. "I told him to just keep working. He's going to play for us, we just don't know when. But he'll be back.

"We're ready. We've kinda anticipated it. We didn't really know, but we'll be ready."

Rivers suggested that Jermaine O'Neal, who sat out a total of 58 games due to left knee soreness that eventually required surgery, would continue to hold down the starting role.

"[Having Jermaine O'Neal is] huge, obviously," said Rivers. "If he doesn't come back -- or Shaq -- we would have some problems, no doubt about it. But having JO back gives us a luxury. That's why Danny went out and signed two guys [in the offseason], so we'd have one. Right now, we'll take it."

Celtics captain Paul Pierce said the focus should be on the players that will be on the court.

"Everybody that's suiting up has got to be ready to play," said Pierce. "You want the big fella to be healthy, you want him to be out there to give us a boost, but the guys that are in uniform, out there playing, it's all we can worry about right now.

"We can't use [Shaq's absence] as an excuse. We've won games without the big fella in the middle. The guys that are going to be out there, those are the guys that matter right now, until Shaq can get healthy. So we can't use that as a crutch to lean on when things don't go right. We have more than enough in that locker room to win this series."

Chris Forsberg covers the Celtics for ESPNBoston.com.