Here were the Celtics shooting blanks, with Paul Pierce, Rajon Rondo and Kevin Garnett a combined 4 for 21 at one point late in the first half, and being crushed on the boards, and yet still very much alive in this Game 5 of the Eastern Conference finals.

Throughout the night, you had to be worried as a Heat fan, considering the moxie and defensive acumen and championship pedigree of this Celtics team, combined with the sterling track records of their stars.

The Heat simply let the savvy Celtics hang around for too long in Game 5, and Boston defended with verve and made the key baskets at the end to take a 3-2 series lead.

“We told our guys, ‘Just hang in there,’ ” Celtics coach Doc Rivers said. “The longer we’re in the game, the better we’ll play.”

Pierce, off most of the night, hit two free throws with 1:34 left to put Boston ahead for good, then nailed a three-pointer in LeBron James’ face to push the Celtics’ lead to 90-86 with 52.9 seconds left. Never could a player feel better about a 6-for-19 shooting night than Pierce, who finished with 19 points.

“He’s a big shot-maker. Always has been,” Rivers said, admitting he didn’t necessarily want Pierce to shoot that three, preferring he drive instead.

Rondo (seven points) made only one basket in the first 43 minutes of the game, then hit two layups midway through the fourth, while steadying the Celtics offense. He closed 3 for 15 from the field but with 13 assists.

“He mirrored our whole team,” Rivers said. In the first three quarters, “we didn’t play very well. We hung around enough until the fourth quarter.”

But the performance of the night was served up by Garnett, who opened 1 for 7 but finished with terrific numbers — 26 points (including two free throws with 8.8 seconds left), 11 for 20 shooting, plus 11 rebounds. Six of his baskets were dunks or layups off passes from Rondo.

“When I had a chance to be aggressive, I was,” Garnett said. “I let a lot of the offense come to me. I take a lot of pride in my craft. I’m a true professional.”

Said Rivers: “He’s just terrific. He has a calming effect on our guys.”

Ray Allen (13 points) shot just 2 for 9 but was 8 for 8 from the line, including two free throws that pushed the Celtics’ lead back to four with 13.8 seconds left.

And don’t forget Mickael Pietrus, who hit two big threes in the final 6:01.

The Celtics were outrebounded 49-39 and shot 40.7 percent, but held the Heat to 39 percent shooting. Considering their woeful first-half shooting (33.3), you would have expected the Celtics to be down a bundle. But thanks to swarming first-half defense, they climbed back from an 11-point hole and trailed by just two at halftime.

“If you looked at the shots we missed, they were our [typical] shots,” Garnett said. “We weren’t discouraged by that. For 48 minutes, we played defense, and it fueled our offense.”

A 9-0 Heat run left the Celtics down 59-50, but Boston closed the third on a 15-1 run. The Celtics again went cold and fell behind 78-72 on a 9-0 Heat spurt.

But Boston responded, in no particular order, with the two Rondo layups, the two Pietrus threes, a Garnett jumper (after he blocked LeBron James at the other end), the Pierce three and 6-for-6 free throw shooting in the final 1:34.

“We’re just a good team,” Rivers said. “I told them, ‘We’ve done nothing.’ We’re playing a heck of a team. They’re not going to give it to us. We have to go get it.”