PHILADELPHIA – Kevin Garnett yapped his way down the court after big baskets and clearly enjoyed taking it to the Philadelphia 76ers.

Rajon Rondo pushed the ball and relentlessly attacked the lane.

Paul Pierce gutted out a knee injury and grinded his way to the free-throw line.

The Boston Celtics hear the whispers that they’re too weary and too old to win another championship, yet continue to prove it’s still too early to count them out.

Garnett scored 27 points, grabbed 13 rebounds and used a dominant second quarter Wednesday night to help the Celtics beat the 76ers 107-91 and take a 2-1 lead in the Eastern Conference semifinals.

Whistled for a costly illegal pick late in a Game 2 loss, Garnett crushed the Sixers early and never let them think about a fourth-quarter rally.

Garnett scored 13 of Boston’s 32 points in the second quarter and the Celtics became the first team to win by double digits. Game 1 and Game 2 were each decided by one point.

Rondo had 23 points and 14 assists. Pierce, playing with a banged-up knee, had 24 points and 12 rebounds.

Game 4 will be Friday night at Philadelphia.

“We just wanted to come out and establish who we are as a team,” Pierce said.

That started with making Garnett a focal point.

Garnett had become forgotten in Boston’s offense in Game 2 until the fourth quarter. Coach Doc Rivers said the Celtics simply weren’t going to him. They wouldn’t let that happen again.

The Celtics needed Garnett at his best in Philadelphia, where the Sixers had won their last four postseason games.

So much for that minor streak. Garnett made 12 of 17 shots and helped Boston outrebound the Sixers by 11 on the defensive boards. He buried those 10- to 16-footers with ease in the second quarter to turn a seven-point deficit into a 13-point lead.

“He got the ball in his spots,” Rondo said. “He hit a couple of fadeaways. A lot of those guys are smaller than him, so he was just able to turn around and shoot over them.”

Pierce had an MCL injury in his left knee rob him of his jumper and slow him on both sides of the ball. He scored only 21 points combined in the first two games and failed to be the impact player the Celtics need to play deeper in the postseason.

All that changed in Game 3. He charged the lane in the first quarter for a couple of dunks. He even pounded the backboard for emphasis after one as if to show the Sixers he still had lift in those legs.

“That’s who he is,” Rivers said. “That’s how he’s been even when he’s healthy. Paul’s just a grinder.”

He’ll need to do it again to hold off the Sixers.

Thaddeus Young scored 22 points and Jrue Holiday had 15 for the Sixers. Lou Williams and Jodie Meeks each scored 13. Starters Elton Brand, Spencer Hawes and Evan Turner combined for only 11 points.

“Sometimes you’ve got to take it and go with it and come back the next game,” Young said. “That’s what we’ve got to do.”

Young scored three baskets and the rest of the Sixers had only two in the second quarter.

“We ran into a Celtics team that had a real sense of purpose about them,” Coach Doug Collins said. “You could see in moment one, they were looking to push that ball in every situation.”

Garnett tortured them from long range and toyed with them from inside

“Our offense finally came alive,” Pierce said. “We moved the ball. We knew that’s what we were going to have to do to score 100 points.”