Brett Brown raised his left hand, looked at it, and said, “There’s night."

Brown raised his right hand, looked at it, and said, “And there’s day.”

He paused.

“It’s Joel Embiid!”

The question: What is the difference between implementing a game plan that doesn’t include Joel Embiid, and one that does?

The answer: It’s everything.

The problem: The uncertainty is routine.

Embiid wound up starting Game 2 against the visiting Nets, and he scored 23 points, 13 of them as the Sixers separated themselves in the third quarter and eventually pulled away for a 145-123 victory. He also yanked down 10 rebounds, all in just 20 minutes of engaged, dominant play. He even left the bench, took a towel across the court and wiped the ball off during a stoppage in play.

He was, at times, magnificent.

“I was out there playing for my teammates," Embiid said afterward. “Sometimes, they need me. Playing through the pain."

To be clear: All the time, they need him. He’s just not always available.

That’s the story of Embiid’s five-year career: a timeline of injury, load-management, and last-minute availabilities punctuated by moments, or even months, of magnificence. Including playoff games, Embiid entered Monday night having played 167 of a possible 421 games, or a little more than 40 percent. He played with a minutes restriction in at least 25 percent of those 167 games.

So, once again, 90 minutes before Brown would lead his team into its second playoff game, he wasn’t sure if his best player would play. The Process was interrupted. This time, Embiid is hobbled by worsening left knee tendinitis. A brain trust of medical types would consult with Embiid, Brown said, to decide whether he would play Monday night.

“Same old same old,” Brown said. “There is a group of people as per usual — doctors, just a handful, a committee, a small handful of people, in collaboration with Joel, always come back and always give me the answer.”

Night.

Or day.

From owner Josh Harris to Daniel Medina, the team’s top doc, to general manager Elton Brand, to Brown on down, there were lots of people with eight crossed fingers and eight crossed toes before tip-off against the Nets. Just another night of gambling with the injury gods.

“That belief, with Joel, and our management and owners and so on — we’re in a stage where we’re buying time,” Brown said. “Can we get a win, and buy a few days? Can we get another win and buy a few more days. You might lose, but you’re alive; buy three more days."

What can you do?

“This is just the path that we are on with Joel.”

It’s a rocky road.

Embiid’s thoughts? Well, despite NBA rules to the contrary, Embiid did not make himself available before the game. But then, he never does — even when he’s not self-evaluating his injury. Such is the privilege of princedom.

Instead, he lets his coach take the heat. And the coach has become inured.

“Let’s face it: It’s not ideal," Brown said. “I have been used to this. Whatever it takes with Joel, in relation to his health — I’m so far past the anxiety of knowledge in relation to [the fact that] you could be given information late."

Embiid’s sudden exclusion or surprise inclusions no longer cause Brown stress. He no longer says, " ‘Oh, now what?’ I’m numb to it. I’m past it. But this is where we’re at."

But where are they at?

They’re a No. 3 seed against a No. 6 upstart, but, thanks largely to Embiid’s injury, the starting five have played together in just 12 of the 29 games since Tobias Harris joined the team.

They are 9-3 in those games.

With Embiid un-whole and unfit, can the Sixers learn enough about this group’s chemistry to offer extensions to Harris and Jimmy Butler? Can they gauge how much of a liability Ben Simmons’ shooting will be long-term? Can they determine if Brown is the right coach for this franchise? Can they asses whether the flurry of asset-depleting moves by first-year general manager Elton Brand made the team better --or just older?

Most important: Can they decided what Embiid really is -- workhorse, or show pony?

Embiid, at 7-foot-2 and 280 pounds, is built like a lion, but he’s as fragile as a kitten. Drafted third overall in 2014, he has yet to play an entire season healthy or enter a postseason at 100 percent. He’s virtually never been in peak condition; injuries, they will tell you, have mainly been the cause of that.

“There’s no doubt: He is our crown jewel,” Brown said, with a verbal shoulder shrug. “This is how I see the world nowadays.”

He sounded, at best, resigned to this bizarre fate yet again; at worst, exasperated.

Because, usually, crown jewels are hard, like diamonds.

They’re not perpetual game-time decisions.

This is the same knee in which a bone bruise and a torn meniscus cost him 40 games as well as the rookie-of- the-year award two seasons ago.

The Sixers say the tendinitis is unrelated to the knee injury. They also say the tendinitis was not made worse by Embiid’s trip to the All-Star Game in Charlotte. Neither claim makes sense.

Embiid returned from the showcase game, complained of increased pain, and did not play in the next eight games. He missed 14 of the Sixers’ last 24 games, including five of the last seven.

He was limited to 24 minutes in the Sixers’ home loss in Game 1. He scored 22 points but was 5-for-15 from the field, missed all five of his three-pointers and was a minus-17. They lost by nine.

This isn’t meant to question Embiid’s toughness. It’s meant to question his durability. Toughness involves pain endurance and compensation and guts; Embiid has all of those. Durability involves the capacity of the mechanisms of the body to function at a high level for a long time.

Either you’ve got it or you don’t. The difference?

It’s like night and day.