Pierce and Allen (0-for-4 in Game 1) snapped out of whatever ailed them. Pierce did it right away, with seven points in the first quarter, but Allen took a little more time.

The third member of Boston’s Big Three hadn’t scored since hitting a 3-pointer with 8:48 left in the third quarter of Game 7 against Atlanta. Boston finished off the Hawks with just seven points from the Allen, who shot 3-for-12 in the first-round finale.

He missed his first four shots Thursday but scored 11 points in the third quarter, including the first four of the second half as the Celtics scored 10 straight to take a 54-36 lead. The Cavaliers cut it to 12 on James’ only basket of the quarter, but they spent most of the fourth quarter trailing by 20.

“It was good to see Ray get it going. I thought that lifted everybody up on our team,” said Celtics coach Doc Rivers, who called the first several plays of the second half for Allen. “I made a concerted effort. I told the coaches at halftime, ’We’re going to him over and over again. We’ve got to get him going.”’

Allen joked that he had forgotten what it felt like to make a basket.

“I think everybody was relieved,” said the 33-year-old All-Star, who like Garnett arrived in an offseason overhaul that helped the Celtics post the biggest single-season turnaround in league history. “It was as if I was just traded here all over again.”

Cleveland took an early eight-point lead, but the Celtics erased it with Garnett and Pierce on the bench. The Boston subs outscored Cleveland’s 26-4 in the first half; in fact, the Celtics bench outscored the Celtics starters 26-18 in the half.

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The Cavaliers led 21-11 in the first quarter, and they still led by seven in the second before their shooting went cold.

Notes: The Cavaliers switched from the burgundy uniforms they wore in Game 1 to primarily blue ones Thursday. ... Celtics basketball boss Danny Ainge said the NBA has reversed a flagrant foul call against Cassell from Game 1. ... The Celtics went 7-for-16 from the line in first half. ... Sasha Pavlovic was the highest-scoring Cleveland sub, with five points. ... Pierce spent some time on the bench after having the thumbnail on his right hand nearly torn off early in the second quarter. He returned with a bandage. ... Boston’s Kendrick Perkins came out with three minutes left in the first quarter with a bloody nose. He sat out the rest of the quarter trying to stop the bleeding with a towel then returned in the second quarter.

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