BOSTON –– At halftime last night, Doc Rivers had a firm directive for his coaching staff: Get Ray Allen going.

After failing to score a point in the first six quarters of the series against the Cavaliers, Allen insists he wasn’t pressing. Anxious maybe, but not pressing. He missed three shots in the first half but swished several warmups in a row during the halftime break and Rivers told him to stay aggressive.

“I told the coaches at halftime, ‘We’re going to him over and over again. We’ve got to get him going.’ ”

Allen missed his first shot but then shook loose for a layup a minute into the third quarter. Sure enough, the bunny opened the floodgates. Allen poured in 11 points in the quarter and finished with 16 in the second half.

“It’s just one of those flow situations for me,” Allen said. “I felt good. Even last game I felt good. The first shot (of the game) I thought I got fouled on, but you get to a point where if you start worrying about missing shots you start pressing. I just let it come to me and then attack when it happens.”

With Allen joining the party, the Celtics pushed a 44-36 halftime lead to a dominating 70-51 after three. Paul Pierce (19 points), Kevin Garnett (13) and Leon Powe (11) also reached double figures.

“I don’t let it get in my head,” Allen said. “People ask if I’m in a slump. You just miss. You can miss four in a row and you can make four in a row. That’s my mentality. Just always continue to put that next shot up.”

Allen dresses next to Rajon Rondo in the team’s locker room. He noted that he attempted only four shots in Game One and cracked, “I guess I have to get my point guard here some flowers or something.”

kmcnamar@projo.com