Joel Embiid says he couldn’t jump in Game 4. His injured knee will decide the series. | David Murphy

ATLANTA — As Doc Rivers sat behind the postgame microphone, he looked and sounded like a man without answers. That’s not a comfortable position for a coach, and he dealt with it the way most coaches do. He blamed missed opportunities and poor ball movement. He critiqued his players’ mindset, and the decisions that they made. He said they’d been outworked. He focused on all of the things that were within the 76ers’ control, and he insisted that they were the reasons that they frittered away an 18-point lead en route to a 103-100 loss to the Hawks in Game 4 Monday night.

Joel Embiid? The knee? The trip to the locker room in the first half?

“I know something was bothering him, but I don’t know what it was,” Rivers said before shifting the focus elsewhere.

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He knows better, of course. He won’t admit it to the public. He might not even admit it to himself. But the Sixers are at an inflection point, and it has nothing to do with the fact that this Eastern Conference semifinals is tied at two games apiece. Their most important player has little more than a leg to stand on. Their most veteran starter is gone for the rest of the series. They have no clear solution for either situation. The things that they can control are minor concerns compared to the things that they can’t.

The reality is that the Sixers win Game 4 going away if they have a healthy Joel Embiid. Did they miss Danny Green? Sure, and they will continue to do so. Furkan Korkmaz started in his place, and finished the night at minus-13. Matisse Thybulle missed four of the five three-pointers he took. Offense, defense, doesn’t matter. Wherever they turn, the Sixers are sacrificing significant production on one end of the court. Again, though, it’s a secondary concern. The big one is the big guy with the balky right knee.

“There’s no excuses. I’ve got to do better.”

It’s been six quarters now since we saw the version of Embiid that was playing basketball as well as any center had ever played it. If you were charting his progression, you would be drawing a line sloping steadily downward. In the second half of Game 3, he was wincing and grabbing his leg. In the first half of Game 4, he was seeking treatment in the locker room. After he returned, he was as mortal a man as we’ve ever seen. He missed all 12 of the shots that he took from the field in the second half. He didn’t come close to converting a golden opportunity for a go-ahead layup with 8.8 seconds left. He finished with 17 points on 4-of-20 shooting and turned the ball over four times.

“He missed good looks,” Ben Simmons said. “It happens. It is what it is. We need to make it easier on him.”

A problem is what it is. The problem. If they didn’t know it when they were out there, they’ll know it when they look at the tape. But they knew it. They had to. There’s just nothing they can do. Embiid is a shell of himself right now. He can’t jump. He can’t change directions. He can’t drop step or spin or rise into his jump shot. He can’t even go up for a game-tying layup the way he normally would. There’s just nothing they can do.

After the game, Embiid tried to hold the party line, but he was like Rivers, and Simmons, and everybody else who spoke. He knew what the deal was. It’s just harder to talk around the question when you’re the one who’s hurt. The last bucket that he missed? The one with 8.8 seconds remaining and the Sixers down one and Tobias Harris setting him up perfectly off a pick-and-roll? That wasn’t a bad night. It wasn’t a miss. It was a guy who tried to use his right leg to lift off and then realized he couldn’t.

“It was a great look, I just didn’t have the lift,” Embiid said. “Thought I got fouled too. But usually I would go up and try to dunk it, try to get fouled and get an and-one. But I just seemed to not be able to, you know, jump, for obvious reasons.”

He’s right. It’s obvious. To everyone. Including the Hawks. You saw it in the way they attacked the paint throughout the second half. You saw it in the way an undersized big man like John Collins dominated the offensive glass. You saw it each time Embiid tried to work himself to the rim on the offensive end.

“I thought from the beginning of the game, even before I went back to the locker room, I just felt like I didn’t have it tonight,” Embiid said. “You could see from the beginning of the game. It was tough. You could just tell. And if I’m not dominating, especially defensively, it’s easy to tell. I’m sure they saw it.”

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The question now is the same as it was after Game 3, when even a blowout win could not obscure Embiid’s deteriorating condition. Now, the series is tied. If Embiid’s knee continues to limit him the way it did in Game 4, their next two victories will be their most difficult of the season.

“It happens,” Embiid said. “Bad games happen. I’ve been playing well. Sometimes, you just can’t control it. I thought in the second half a bunch of shots went in-and-out. A couple calls that could have gone either way. I can do better. I can always do better. But as far as being 100 percent, I don’t think that’s gonna happen until the year is actually over. I just have to go out and manage it.”

From the beginning, the Sixers said it would be a day-to-day thing. Heading into Game 5, the reality is finally settling in.