Jonathan Lewis can’t extend a hand to shake. It’s soaked in sweat, with a tinge of blood.

A little earlier during a scrimmage drill in training, Lewis, a 21-year-old forward for New York City FC, got his foot to the ball in front of the net. His shot sailed past goal. Momentum taking control, Lewis flew into a swan dive, skidding past the end line. He slammed his hands on the ground and let out an expletive.

Lewis is full of potential, beaming with energy, his ambition open. Those who spend time around him say Lewis exudes self-confidence. There’s good reason for that.

In two years with NYCFC Lewis has started just four games — none this season. But his play has increased calls from fans for that to change. Lewis has notched a goal and two assists in 10 games — averaging nearly a shot per game despite playing a little more than 18 minutes.

If Lewis earns a starting job, the possibilities are limitless. The U.S. national team. Europe. He already made the USMNT’s U20 team without prior national team experience.

Lewis walked into Akron his freshman year as a relative unknown. He ended up leaving after a season, becoming the third overall pick in the MLS Draft. But going to college was never the plan.

When Lewis graduated high school in Plantation, Fla., he hopped on a plane to England. His intention: “Just train with the team and hopefully they sign me to a professional contract,” Lewis told The Post.

That team was Bradford City AFC, a third-division club in West Yorkshire, a far cry from the Premier League. It was a leap of faith. Lewis had talent, but wasn’t a highly rated recruit. Schools called, Akron being one of them, but Lewis bet on himself.

It didn’t work out.

The problem wasn’t performance-based — Lewis said the Bantams offered him a contract. But he wanted to come home.

“The team that I went to was in League 1,” Lewis said. “And it was a different type of playing style than you see on TV, in the Premier League.

“ … I feel like I wasn’t ready yet.”

The email landed in Jared Embick’s inbox about a year after he had last talked to Lewis.

Things hadn’t worked out over in England, it said. Lewis was considering coming back to school. Was Akron interested?

At this point, Lewis was back in the States, playing at the Chicago Fire’s development academy. Intrigued, Embick, the Zips’ coach, and Leo Chappel, an assistant, went to see Lewis play against the Los Angeles Galaxy’s academy.

“He was just drilling through them,” Chappel recalled. “Up and down the channel. Everything off the dribble. Just a handful. A handful. And he didn’t have much of a supporting cast, but that day he was a man amongst boys for sure.”

So, yes, Akron was interested.

The thing about Lewis’ talent though, is that he knows he has it. He’s not afraid to gamble on it either. Lewis wasn’t a highly rated recruit, Embick posits, because he didn’t stay in one place long enough to get noticed — the lack of patience a by-product of confidence. Before going to the MLS, Lewis played in five different places.

“It’s not really a non-dedication thing, for him, to stay at a team that he got put to,” said Nick Hinds, a childhood friend and teammate at Akron who now plays for the Seattle Sounders. “But it’s just more of finding and searching for a better opportunity for him as a player to strive. If he’s happy at one club and he’s playing well, he’s not going to leave. That’s just how he is.”

That doesn’t mean Lewis wasn’t happy, at Akron or elsewhere. But it does mean he continually looks for better opportunities, waiting for one that will let him break through.

With the Zips, that manifested itself in the locker room, where Lewis was a loud presence right away. It didn’t help him start off on the right foot.

“ I think with some teammates [it was an issue],” Embick said, “because you don’t know him when he shows up in August and you’re trying to learn about him, this or that, and here he is, he’s going to sit here and tell you he’s going to score 15 goals and dominate.”

Lewis didn’t score 15 goals at Akron, but he tied the Division I lead with 12 assists and won Mid-American Conference Freshman of the Year. His stock rose high enough to go in the top-five of the MLS Draft and earn a spot with the U20 USMNT. Keeping with a general theme, he left Akron after one season.

Lewis is standing along the sideline of NYCFC’s practice facility after training, going over his well-traveled career in a relatively short amount of time. It took as many career stops to get to the MLS as he may have from here on out.

That chance earlier in practice — he should’ve made it, and he knows it. Finishing has been an issue for him before, but in that moment, he wanted more from himself. Growing up, Lewis says, he was one of the worst players on his team. He sets high expectations.

Now, he’s on the verge of another breakthrough. With that comes bigger, better opportunities.

Whether he starts or not, there will soon be a decision to make about his future. He’s no stranger to that. He’s open to possibilities.

“I think that everybody wants to go to Europe,” Lewis said. “So of course my end goal is to play in Europe. But I have to take it one step at a time, so right now, New York City’s my focus.”

For now, that means finishing chances and breaking the starting lineup. The future can wait.

Asked where he sees himself a year from now, Lewis stalls for a brief second.

“Ah, I don’t know, honestly,” he says. “I just have to keep working. Hopefully my ability, my hard work can just lead me on to whatever’s next.”

In Lewis’ world, that could mean anything.