It's time for the subs to rise

The Celtics assistant coach had Leon Powe, Mikki Moore, and Glen Davis at one end of the floor at the team's practice facility yesterday, studying as he mimed picks and pump fakes, stepped to the spots he figured Brad Miller would go to, and pointed to parts of the floor where he expected the three of them to be in games.

Every motion came with an explanation that sounded like computer coding.

Something, something, something . . . flash defense.

Something, something, something . . . he's going to try to move you back.

Something, something, something . . . we've got to all be together.

Powe nodded confidently. Davis looked like he not only learned it, but could write a paper about it. The look on Moore's face said he was still processing it all. He asked questions, until it became clearer. They bounced concepts around until they were on the same page.

In the two months during the regular season when a right knee injury kept Kevin Garnett off the floor, it was OK for them simply to be in the same book. But early yesterday morning, when word spread that Garnett's knee would likely keep him out for the playoffs, they realized that wasn't an option anymore.

"I woke up," Powe said, "flicked through the channels, and was like, 'Hold up, what?' "

Davis found out the same way. Kendrick Perkins made it sound like he had heard not long after arriving at HealthPoint.

"You can only hide it for so long," Perkins said. "I think we tried to cover it up a little bit, but we know he's not healthy. We know he's not going to be able to play in the postseason."

What Perkins acknowledged was that as much as expectations will rise for stars Paul Pierce and Ray Allen when the first-round series against the Bulls begins tomorrow afternoon at the Garden, the Celtics have just as much riding on what is now a frontcourt-by-committee.

"It's a lot to put on the team," Perkins said. "I think it's more pressure put on the bigs than anything. It's some big shoes to fill."

"We're talking about KG here," said Davis, who will likely take Garnett's place in the starting lineup. "KG not being here, it's huge shoes. I think with the guys coming off the bench we can fill it all together. We're no KGs, but we're going to go out there and do what we do and at the same time do what's best for the team."

"It's going to be tough," Powe added. "He brings that intensity on defense and that energy that we need, but with one person down our motto is to get it done anyway."

Skeptical of Garnett's status, Bulls coach Vinny Del Negro said, "Perkins has hurt us. Leon Powe. Glen Davis. Mikki Moore. They have a very strong team. Kevin missed 20-some games and they still won 60-plus. They're the defending world champs. They're battle-tested."

It's easy for Perkins to see the difference in the Celtics without Garnett.

"We've been scoring a lot of points without KG, but we've been giving up a lot of points, too," he said. "We've just got to get back to playing defense the way we can play defense."

Garnett and Perkins communicated on the floor, guiding the defense. Perkins said that's hard to replicate.

"You can try, but it's not the same," he said. "You can try to communicate with those guys and hopefully you'll be on the same page with them, but once you have a bond on the court it's kind of different. Me and KG just had this bond where he knew I was going to be there. I was going to be there. It was a serious trust factor."

Powe dealt with his own late-season injury, but since Garnett's absence, the Celtics' backup big men have developed their own dynamic on the court.

"We know what to expect together," Davis said. "We have a camaraderie out there as far as bigs, what we can do, what we should do, and how we need to play together out there. We've just got to apply it in the playoffs."

Signed in late February to be this year's version of P.J. Brown, Moore is still getting integrated, and now will have to play a larger role. Teammates see him pressing to pull everything together.

"Mikki, to me, was one of the guys that's key because he's still trying to figure out and understand what we need to do here," said Allen. "I sense his frustration level, that he wants to do everything right, perfect. I told him, 'Just go out there and play hard and play smart. Don't think, just play basketball.' "

When Moore picked up his fifth foul late in Wednesday's regular-season finale against Washington, he was visibly frustrated as he walked to the bench. But before Moore left the floor, Davis said a few words to him. They nodded as if they had an understanding.

"We've got to make sure we're talking to each other," Powe said. "Just seeing eye to eye with each other on the defensive end. That's the key part. That's what Kevin was doing when he was controlling the paint."

Knowing how much of a difference it makes, Perkins charged himself with that responsibility.

"It starts from me," he said. "I've got to do a better job communicating everything. I've got to talk to the defense. I've got to be the anchor. I've got to make sure guys are in their right spot and guys are talking.

"Everybody's got to be on the same page."

Julian Benbow can be reached at jbenbow@globe.com.