There were seven seconds left and the Celtics were holding a three-point lead when Paul Pierce missed a 20-foot jumper. The smart play is to commit a foul, put Philadelphia on the free throw line and bleed those precious seconds off the clock.

It’s an obvious tactic that so many NBA teams screw up, or they simply fail to do anything at all and take their chances that their opponent will miss a 3-pointer. It’s the equivalent of crossing the street in traffic and hoping the car stops. The Celtics almost always foul, but in the heat of the moment …

“We yelled,” Celtics coach Doc Rivers said. “We were yelling, Foul! Foul! Foul!”

Rajon Rondo heard none of this, not that he could have with the Garden crowd roaring in full throat. Instead, Rondo was flashing back to the end of the Sixers last game against Chicago when they didn’t call a timeout and instead rushed down the end of the court.

“I didn’t hear it honestly,” he said. “I didn’t hear anything. I was just trying to make the right decision.”

Seeing Philly guard Jrue Holiday dribble up the court, Rondo gave the foul after he crossed halfcourt and put Holiday at the line with 3.2 seconds left. Holiday made both, putting the Sixers down one, which was entirely the point.

“Well, when they got the rebound I took a glance at the score,” Rondo said. “We were up three and I knew a two couldn’t beat us and I felt pretty good about rebounding [an intentional miss] so I just decided to foul.”

“Rondo is so smart,” Rivers said. “He was going to do it anyway, but we talk about it. We work on stuff like that in practice. And it was perfect because it allowed them to get across halfcourt to use more clock. You know, it couldn’t have been done any better and it was a great play by Rondo.”

Rondo had one more bit of late-genius in him. The Sixers still had a foul to give and seeing Evan Turner guarding him, Rondo took the inbound pass and ran the other way. “I felt like I could out-quick him,” Rondo said. “And that’s what I did.”

“I think sometimes his basketball intellect is overshadowed by some of his moments,” Keyon Dolling said. “He’s the smartest player in our game. If you look, he’s a coach on the floor. I watched him the whole last five possessions, and he was just coaching everybody. It kind of reminded me of Doc, the way he was calling each person, getting the eye contact, telling them what to do, telling them what to look for. It’s pretty amazing to see him on the court. He’s not so quiet and reserved when he’s dictating policy on the court.”

So much went into the Celtics’ 92-91 victory over Philadelphia in Game 1 of the Eastern Conference semifinals. They fought back from a 10-point first quarter deficit that grew to 13 in the second quarter and while Philly kept answering, the Celtics somehow found a way to have the last word.

Kevin Garnett was magnificent again with 29 points and 11 rebounds. Rondo hit the turbo button in the second half and recorded another triple double with 13 points, 12 rebounds and 17 assists. Ray Allen wasn’t even sure if he would play Saturday morning, but he fought through the pain and delivered 12 crucial points off the bench. Avery Bradley made two huge defensive plays and reminded everyone why the second-year guard has been such a difference-maker.

Beyond the individual brilliance, what it came down to, ultimately, was execution and strategy. The Sixers were having their way with the Celtics late in the third quarter, thanks to Spencer Hawes and rookie big man Lavoy Allen, who carved them up on pick and pops. They tried Brandon Bass. They tried Greg Stiemsma and Ryan Hollins. When none of those options worked, Rivers switched to a small lineup with Paul Pierce playing power forward and Rondo, Bradley and Allen surrounding Garnett.

For the last two days, Rivers kept saying he didn’t want to turn the game into a track meet, but the Celtics beat Philly at its own game, getting 14 fast break points to 13 for the Sixers.

“Well, we wanted to run,” Rivers said. “I mean, whenever I say that, I’m talking about them. Really. I told our guys over and over again. We don’t want them to run. We want to run every time.”

Because they are the Celtics, they had to make it tough on themselves. They started out in what they call “random,” which are basically sets without plays. Rivers thought they were in it too much. Rondo thought they were getting good shots, just not making them. As always, the creative tension lies at the heart of their relationship.

“I thought he was searching for what to do early on, how to attack,” Rivers said.

Rondo made the adjustment. After scoring just two points in the first half, he took over in the second. Those jump shots he made at the end of the game? Those were originally called for Allen, but Rondo wanted them and he buried them. He wound up scoring 11 points in the second half with eight rebounds and nine assists.

Asked later for his thoughts on the triple double, Rondo said, “I didn’t get a nap today so I didn’t know what to expect. I was trying to struggling with my shot early and I was turning the ball over, so I was trying to do everything I could to help my team. And I came up with some rebounds, I came up with some assists and it just happened to be a triple double tonight.”

Quintessential Rondo, but don’t sleep on his late-game decision-making. That’s what ultimately pushed them over the top in a hard-fought first game.