Philadelphia center Joel Embiid tries to pass the ball while pressured by the Celtics’ Jayson Tatum, right, and Marcus Smart during the first half of Game 2 of the Eastern Conference semifinals on Wednesday in Boston. AP Photo/Charles Krupa

Jayson Tatum was on the bench with four fouls at the start of the fourth quarter. He had seven points in just over 19 minutes on the floor, making just one of seven field goal attempts to that point.

He was essentially done for the night.

More trouble in paradise for the Green team? Hardly.

The Celtics were actually in cruise control at that point. They were still blowing out the Sixers. They took a 27-point lead into the final quarter, and didn’t look back.

After their dismal effort in Game 1, losing with Joel Embiid in street clothes, this type of performance was a must if their expectation is to get back into the NBA Finals and finish the job this time.

So with their backs against the wall, they rallied in a big way to avoid going down 0-2. They crushed Doc Rivers’ team, evening the series with a 121-87 win.

All of which begs the question: Why can’t they play like this all the time?

Why can’t they just keep their foot on the gas?

They certainly have the ability. They have the talent and depth to run away with just about every game if they put their minds to it, and as we saw, even with Tatum buried with foul trouble.

“I’m convinced that we have a great locker room and a great team, and that when we play to our level, we have a chance to win,” Celtics Coach Joe Mazzulla said after the win. “So we just have to keep that.”

Playing to “our level” hasn’t been a constant, and until they solve that problem, it’s going to be a struggle.

Tatum seemed to be the only player who was out of sorts in Game 2. Putting up that kind of stat line won’t do them any favors going forward. Even having a legitimate co-star in Jaylen Brown, and the best sixth-man in the league in Malcom Brogdon, Tatum no-shows won’t be the recipe for success the longer the playoffs go.

That said, the Celtics still had plenty of ammunition to rub out the Sixers with room to spare en route to evening off the series.

Brown (25 points) delivered. So did Brogdon (23 points), Derrick White (15 points) and Marcus Smart (15 points), who provided enough offense to get the job done.

With Brown setting the tone and doing most of the damage in the first half, that group essentially poured it on in the third quarter, outscoring the Sixers 35-16, while hitting no speed bumps the rest of the way.

Payton Pritchard and Sam Hauser were in the game midway through the fourth quarter. Mike Muscala and Luke Kornet joined them with five minutes to go. That’s how much of a laugher it was.

While it might be easy to say the Sixers already accomplished their mission by taking a game in Boston, and didn’t have the same intensity in Game 2, that wouldn’t be totally fair to the Celtics, who got out to a double-digit lead early in the second quarter, played great defense, and pretty much coasted from there.

With Embiid returning to the lineup, the Sixers had a chance to step on the Celtics’ throats, and put themselves in the driver’s seat heading back to Philadelphia. They had a chance to put the Celtics in a dubious 0-2 hole. That should have been incentive enough.

But adding Embiid (15 points) didn’t provide much of a boost, while James Harden (12 points) returned to being mortal after donning the cape and carrying the Sixers in Game 1 with his 45-point effort.

Rivers’ crew basically hung in for a half, down by just eight, but couldn’t match the Celtics in the second half.

The Celtics basically buried them with a barrage of 3-pointers with Brogdon (6 for 10), (Brown (3 for 6), White (3 for 6) and Grant Williams (4 for 8) throwing down a series of bombs.

While the Celtics didn’t take many 3’s in the opening loss (26), they nearly doubled that by hauling up 51 in Game 2, making 20 of them. They also cut their turnovers down, with only six, compared with 16 in Game 1.

Can’t score against a zone defense?

They shot down that theory, too, while also playing a better brand of defense themselves.

Before the game, Mazzulla said the formula for beating a zone was simple enough.

“You just have to shoot the ball when you’re open … shoot it. Make it,” Mazzulla said.

They shot, and shot, and eventually, found their rhythm.

Ultimately, it wound up a rest night for Tatum, who, as mentioned above, still needs to be a factor going forward. The Celtics did the job without him, essentially. But when it really gets down to the nitty gritty, Tatum has to rise.

If anything, that’s the one remaining question when it comes to the Celtics. Can Tatum take it to the next level when push comes to shove in the postseason?

Stay tuned on that front.

For now, their Game 2 performance was encouraging. The Celtics are a tough team to beat when they have it going on all cylinders.

“This is one game. They came out great and played a great game in the first one. James (Harden) played great,” said Brogdon. “I thought tonight we flipped the script on that, we did a great job on him and a great job overall. But that’s one game. It doesn’t mean anything if there’s no carryover.”

They’re capable of performing this way just about every game. But for whatever reason, they haven’t been able to make it easy on themselves.

Even with Embiid, who is now 1-9 against the Celtics in the postseason, the Sixers still aren’t in the same area code as the Celtics.

If Tatum gets back to being Tatum, and this version of the Celtics shows up every game, they should roll past the Sixers. And whoever’s up next.