Paul Pierce is working very hard to inspire his teammates.

Journal / Glenn Osmundson

WALTHAM, Mass. — At the end of every Celtics practice, the players gather in a circle and raise their hands to form a giant fist. Yesterday, the captain, Paul Pierce, talked about opportunity.

“We’ve got a tremendous opportunity. Now we’ve got to go out and make the most of it right now,” he said.

“I told the guys before we broke we’ve got a great opportunity. We don’t get this opportunity too much in our careers. We’ve got to go out there and play like it’s our last because you’re never going to know when this is going to happen again.”

Pierce should know. This is his 10th NBA season, his fifth trip to the playoffs and his second to the Eastern Conference finals, the first coming in 2002.

“It’s been six years since I’ve been in the Eastern Conference finals and my second time in 10 years. So this opportunity isn’t guaranteed. A lot of players don’t even make it that far. It’s a tremendous opportunity, and I want these guys to realize that,” he added.

Veterans such as Kevin Garnett, Ray Allen, P.J. Brown, James Posey, Sam Cassell and Pierce understand that. Young players like Rajon Rondo and Kendrick Perkins are still learning.

“I don’t know if the young guys ever get that,” coach Doc Rivers said. “They always think there’s another opportunity and another opportunity. I found it interesting reading (Antonio) McDyess’s statement about how spirited he’s been playing. He’s basically said this might be (his) last shot. I think veterans really get that. They understand that. I don’t know if young guys do until later.”

McDyess scored 21 points Monday night, and spoke about his approach to the game this season.

“I’m almost to the end of the road . . . I’m at the end of my career, and I just feel like leaving everything out on the floor. There won’t be any excuses,” he said.

Quick start imperative

A fast start is important tonight. Pierce noted that the team that gets the early jump usually wins, and defense is a key.

“It’s the defense. It’s the hustle plays. They came out here diving for loose balls, making all the energy plays. That’s what really got them going. So we’ve got to see that and go out there and do the same things from the jump. We can’t ease our way into it. We’ve got to do it right from the jump,” he said.

The Celtics must respond to Detroit’s improved defense in Game Four.

“We’ve got to pick up our defensive intensity now. They picked it up so we’ve got to go to another level. That’s what this series has been all about. The team that’s played defense, the first one to play defense, is the team that’s going to win. We’ve got to pick up our energy level,” Pierce said.

Rivers had a slightly different take.

“It’s important,” he said of the start, “but the whole key is ending the right way. We didn’t get off to a fast start yesterday, but we had many chances to win the game. We were down five, down three in the fourth quarter. We didn’t play well, clearly, but through all that, when you watch the tape, we still had chances.”

Mood always upbeat

So what exactly do the Celtics do at practice these days?

“Watch a lot of film and make a few defensive adjustments,” Rivers said.

After they broke yesterday, Pierce talked to the media mass, sitting at first but then insisting on standing in his regular spot against the wall.

On the court, Perkins worked on short jump shots from both sides of the basket, three ball boys feeding him passes. Rondo practiced jump shots, mostly from either baseline. Two ball boys rebounded and passed him the ball. Brown and Leon Powe practiced free throws. Kevin Garnett disappeared into the training room. Cassell and Allen usually play one-on-one, but not yesterday.

The mood is always upbeat, a tribute to Rivers and his approach to the game. As Pierce said, all season the Celtics have stayed loose, not too high after a victory and not too low after a defeat.

mszostak@projo.com