PIERCE

BOSTON — Celtics coach Doc Rivers was expecting his guards to fight through picks last night so Antonio McDyess, the veteran who tortured them for 21 points in Game Four, wouldn’t be so open.

“We’re over-helping a little bit,” Rivers explained. “Our guards have to get over screens that are not only just pick-and-rolls but single doubles because it’s forcing our [big guys] to stay longer than they should. Unfortunately for the bigs, it looks like the bigs aren’t doing their jobs, and a lot of times that’s not the case. It’s the guards not fighting over the screens, and that’s forcing the bigs to stay.”

One of those bigs, Kendrick Perkins, said the Celtics can live with McDyess shooting but not with other Pistons scoring as well.

“McDyess can’t hit that shot and we give Rip (Richard Hamilton) 20 and Rasheed (Wallace) 16. If McDyess throws his 21 on us, we got to shut everyone else down. What it is, is we’re trapping, and McDyess is wide open.”

Perkins is wise enough to understand that “if you’re going to take something away, you’re going to end up giving up something. So if we’re going to take away Rip, that’s what it’s going to be.”

McDyess is averaging 9.4 points and 7.7 rebounds in this series. Detroit coach Flip Saunders said he was the second or third option on offense, and if he doesn’t make his shot, the defense looks great. If he does, he and the Pistons coaches look good.

‘Must game’

Paul Pierce considered last night’s Game Five a “must game” for the Celtics, and Rivers agreed, sort of.

“I think they all are. That’s the only way I look at it. I like that mentality. I think we should have it every night,” he said. “It’s a big win obviously for either team. Game Fives and Game Sevens are very similar. Big swing games.”

Heading into last night’s contest, the Celtics had won the four big swing games in the Atlanta and Cleveland series. What’s the secret?

“I really don’t know the answer because, again, we’re still new to each other in a lot of ways, but they have been able to have a single-minded focus in big games. They’ve proven that. They’ve won two Game Fives and two Game Sevens already, and I think that’s important. … But then again, you just can’t rely on that. You got it back — the home court — and that’s what you wanted. Now you have to take advantage of it,” he said.

Complimenting Perkins

Energy from role players and the bench brigade is critical to a playoff run, and Perkins drew special praise from his coach.

“When you’re a role player, energy has to be a part of what you bring to the game,” Rivers said. “The last two games Perk has probably been as good as he’s been all playoffs in that regard, and he has to keep doing that.”

Perkins’ scoring (6.6 points per game) comes from his energy and movement, his coach said, not from anything the team is doing for him.

“We did show him where he can flood or where he can duck in, but you have to do it with an amazing amount of energy,” Rivers said. “And it’s exhausting because of the 20 times you flood, you get it twice.

“It’s human nature, so you stop doing it. After he stopped doing it, then it showed in the spacing on the other side of the floor. … When Perk floods, he forces someone to guard him.”

mszostak@projo.com