With a potentially historic upset looming for Team USA, Steve Kerr puts the ball in LeBron James’ experienced hands.

LONDON – This had the potential makings of the second biggest and most monumental upset in the history of international basketball.

The first? That’s easy: a young, developing country like South Sudan making it this far, matching up with the vaunted Team USA in a tune-up on the way to the 2024 Olympics.

This is a team built from scratch, and hastily so, and training for these Games outside its borders — there are no indoor courts in South Sudan — that forced LeBron James to go into championship mode Saturday for an exhibition game.

What happened at O2 Arena was a convergence of twin forces. South Sudan played the game of its young life; the team is only a few years old and making its maiden voyage to the Olympics, loaded with refugees from Sudan. And the other team, favored by 43 points, in the words of coach Steve Kerr, “let our guards down as a team and a staff.”

So it was USA 101, South Sudan 100, a game controlled mainly by South Sudan, rescued by LeBron with the game-winning shot with eight seconds left, and tense until the buzzer after a pair of missed chances by South Sudan.

LeBron James scores a game-high 25 points, including the winning basket for Team USA in an exhibition against South Sudan.

It should be mentioned that, as a showcase game, this didn’t count. But try explaining that to everyone involved. Because the way it turned serious in the second half and brought out the best on both benches, it sure seemed like.

“Wild game,” Stephen Curry said. “They played really intense. It was nice to see how we responded. LeBron with a great finish down the stretch.”

South Sudan made buckets — easy ones, tough ones, insane ones, long-distance ones — to build a 16-point lead in the second quarter. The USA struggled from deep, missing 12 of its first 13 shots from range. That’s when the Americans were faced with a decision in the second half: Do they play this one to win, even for an exhibition? The choice was easy.

Kerr used the second unit, which is stronger defensively, to start the third quarter. Anthony Davis’ interior protection and presence changed the tenor. The deficit started to shrink. Over on the bench, LeBron stirred, rose from his seat, did a few stretching exercises in an open space off the floor.

“Look,” Kerr said. “The whole team was embarrassed at halftime. He was not thrilled at me (when I did) not start him in third quarter. I looked down the bench and could see him chomping at the bit to get out there on the floor.”

Once the starters were re-inserted, a sense of order was restored. Jrue Holiday saved a steal from bouncing out of bounds and passed to LeBron for a dunk. Devin Booker tied the game with a 3-pointer with 58 seconds left in the third quarter, then Curry gave USA the lead with a 3.

But South Sudan refused to fade; if anything, the stubborn team stuck close in the fourth quarter and took a one-point lead on JT Thor’s shot over LeBron with 20 seconds left.

There was a hush at the O2 and a timeout by the USA. Both were completely unexpected, exhibition game or not. Where did this come from? How did this happen?

You can start here, about South Sudan: The country gained independence from Sudan in 2011. The next year, Sudan’s most accomplished player, Luol Deng, who fled the civil war-torn country when he was 5 and spent much of his NBA career with the Bulls, played for Great Britain in the 2012 Olympics because South Sudan didn’t have a team.

Once a movement began in South Sudan to build a basketball infrastructure, Deng answered the call and became its executive director. The team initially had no funds, so Deng bankrolled it, buying equipment and footing travel.

And it had no players; he had to round up a roster, encouraging players with dual residency in other countries to return to the homeland and become trailblazers.

“When you think about what that team has had to overcome to qualify for the Olympics, I’m really happy for Luol,” Kerr said. “They’ve put together a good team in the face of adversity.”

South Sudan beat 11-time African champ Angola in last year’s World Cup to qualify for these Olympics, becoming lowest ranked team to do so since 2004. It was a dramatic a rise from nowhere for a team with only two back-of-the-rotation NBA players, Thor and Wenyen Gabriel.

And after LeBron went isolation and dropped a driving layup with nine seconds left for a one-point USA lead, South Sudan had the chance to shake up international basketball with one last possession. The sellout crowd at the O2, which earlier chanted “U-S-A”, began shifting its allegiance to the big underdog, if only to witness a moment.

One missed shot, followed by another even closer — Anthony Edwards might’ve gotten away with an arm grab — caused great hopes to become dashed.

Carlik Jones, a guard who had a brief journeyman NBA career, posted a 15-point, 11-rebound, 11-assist triple-double and proved a handful all night for the USA. Gabriel, LeBron’s former teammate with the Lakers, played well with 11 points, as did Marial Shayok (24 points). Again, this isn’t a stacked team, but a determined one.

“The ending was good for us,” Kerr said. “A good reminder that when we play against teams, it’s the biggest game of their lives. This was the first game where we felt it was in doubt. It’s good for us to feel it now. We’re going to feel it again. It’s good to be challenged.”

The decision to go with LeBron on the last possession was strategic.

“We wanted to give him the ball,” Kerr said. “We had some options. But the idea is to get LeBron downhill. He’s just got such a competitive spirit.”

LeBron scored 25 points in 23 minutes and was steady when his teammates were not. Davis had another double-double off the bench. Curry was the only USA player who wasn’t frigid from deep, finishing 3-for-9, and nailing a key 3-pointer late.

Kerr remained diplomatic after the close call.

“If we don’t play the right way don’t come with the right energy and focus, we can be beat, no matter who we play,” he said. “But we have that gear and if we can find it, we can overwhelm teams. It was a great reminder of two things — that, and if we don’t play our best, we can get beat.”