Consider Game 2 a scheduled loss for the Sixers and a rehab session for Joel Embiid. Game 3 will be different.

BOSTON — The problem with changing your lineup on the fly is that you don’t get to practice. That’s the situation the 76ers found themselves in Wednesday, when Joel Embiid returned from a 12-day absence, carrying the Michael Jordan trophy but still burdened by a bum knee.

The Sixers weren’t sure he would play until about two hours before Game 2 of the Eastern Conference semifinal. Obviously, they didn’t have time to practice.

So, they held a practice against the Celtics. Essentially, anyway.

They’d held six practices, two shoot-arounds, and played two games learning to function without their ball-stopping MVP, but none remembering how to function with him. And they looked like it.

Consider it live rehab for Embiid, and successful; he emerged with no new limps.

Consider it a scheduled loss. Bank it: The Sixers will be a different team Friday night in Game 3 at home.

“We had a shoot-around today,” to prepare with Embiid, coach Doc Rivers said with a slight shrug. “I figured there would be some growing pains in the first half.”

» READ MORE: ‘Schedule loss’ comment puts Doc Rivers on the Sixers hot seat again. It shouldn’t.

Really, all that matters is what comes next. They stand tied, 1-1, in the best-of-seven series.

“It’ll be easy to see on film. And it will be easy to fix,” Rivers said.

His team’s No. 3 seed was earned with Embiid as their offensive and defensive centerpiece. It’s like riding a bike, right?

“We are what we are. We’ve played all year. That’s not hard to get back to,” Rivers said. “We’ll get back to it.”

Promise?

Doc couldn’t say it but everybody knew: This defeat was inevitable, whether or not The Process was healthy. The margin, too, was unremarkable: 121-87.

Embiid had 15 points, three rebounds, and five blocks in 27 minutes. The Celtics blew it open with a 35-point third quarter, and neither Embiid nor Harden played in the fourth. Again: completely predictable.

The Celtics are the East’s No. 2 seed. They ranked fourth in the league in scoring this season. They were playing at home, and they were more than a little bit desperate, having lost Game 1 despite Embiid’s absence. They rode a facsimile of this year’s offense all the way to Game 6 of the NBA Finals last year. They’re really, really good.

So are the Sixers, both with and without Embiid.

Aren’t they?

Is there a universe in which the Sixers are a better team with Embiid at 0% than with him at 75%, wearing a bulky brace on his right knee under his tights? The Sixers can run an actual practice Thursday, so we’ll find out further whether zero Embiid is greater than lesser Embiid on Friday night at Game 3 in Philadelphia.

The Sixers proved in their previous two games to be much deeper than anyone thought. That’s how they won Game 4 in Brooklyn without Embiid, swept the Nets, and earned a week off. They practiced without Embiid and won Game 1 in Boston on Monday. Harden matched his career playoff high with 45 points. Tyrese Maxey, Tobias Harris, and De’Anthony Melton played complementary basketball against a Celtics team that either was badly matched, badly motivated, or both.

Regardless, the Sixers were never going to win Game 2. At least, not without Harden going off again.

» READ MORE: Sixers overwhelmed by Boston Celtics in Game 2 loss, spoiling Joel Embiid’s return

Harden has scored more than 40 points in a playoff game 10 times. After dropping from 45 on Monday to 12 on Wednesday, he’s averaged 20.2 fewer points in his 10 post-40 playoff games. The Celtics did little to hinder him, he said. The Sixers did more.

“It wasn’t ... our spacing wasn’t right,” Harden said. “We’ve got to do a better job of knowing where we are on the floor.”

The Sixers’ nine-point halftime deficit would have been considerably worse but for Embiid’s five blocked shots, one shy of his playoff high and the first time he collected five in four years. However, the blocks were a result more of Boston’s fearlessness of a wounded lion than of any sort of defensive predation. The Celtics challenged Embiid, he rejected a few, but he also got dunked on twice.

Therein lay considerable hope. As the game progressed, Embiid played with more speed, more power, and more aggression — and, unlike his previous returns from injuries, he never looked exhausted.

“I was a bit surprised. Yesterday was the first time I really did [anything],” he said, referring to his light practice session Tuesday.

He’s learned that diet, rest, and low-impact work in swimming pools can help maintain conditioning.

“I’ve grown a lot. I’ve found ways to take care of myself,” Embiid said. “I thought tonight was fine. It should be better as the days go on.”

It wasn’t bad, really.

Twenty-one minutes into the game Embiid had five blocks and eight points but he still looked a bit ... off. Slow. Cautious. Tentative.

Then, necessity knocked.

With just under three minutes to play in the first half, Embiid set a pick for Harden 27 feet from the basket, straight on, then rolled. Harden hit him with the pass. Embiid caught it, a bit deep, and laid it up softly, but he was going to land on his heels. He did. Awkwardly. And ... he was fine.

Two possessions later, he ran the break and took a hard foul. In the last minute of the half, he spun on Al Horford, sped to the rim, and threw down a monstrous two-handed jam.

At halftime he had 13 points, five blocks, two rebounds, and all of his confidence back.

The same cannot be said for the rest of the team. They looked scattered.

At least they got a practice in.

» READ MORE: Sixers overwhelmed by Boston Celtics in Game 2 loss, spoiling Joel Embiid’s return