At the outset of John Wick: Chapter 3 — Parabellum, Keanu Reeves’ title character goes up against a towering assassin who might look familiar to Sixers fans.

It’s backup center Boban Marjanovic, the 7-foot, 3-inch-tall Serb who arrived in Philadelphia from the Los Angeles Clippers as part of the trade that brought Tobias Harris and Mike Scott.

Turns out Marjanovic has a fairly substantial and memorable cameo in the movie, which stars Reeves as a hit man with a $14 million bounty on his head who finds himself battling the world’s deadliest killers.

And the world’s tallest.

When he was blocking out ideas for John Wick 3, director Chad Stahelski — once a professional stuntman — conceived of a scene that would pit Reeves against a much taller opponent in a very cramped space.

“As an action choreographer, I like to do juxtapositions of men and women, all shapes and sizes, in all kinds of environments. And for this movie, I had this idea of John Wick up against the biggest fighter I could find, in the stacks of a public library, so the guy would barely fit.”

He couldn’t think of any seven-foot stuntmen, and though he knew there were obviously plenty of tall athletic guys in the NBA, Stahelski confesses, “I know literally zero about basketball. But I’m talking to one of our producers who’s this huge basketball fan, and he says, ‘Look, I think I got the guy. He’s this [Serbian] guy who’s done commercials and he’s like 7-foot-8 and he’s got the biggest hands in the NBA. Trust me.’ And based on how excited he was, I was super-interested.”

Still, he insisted on a tryout for Marjanovic.

“So I met him and gave him to the stunt team for two hours so they could evaluate him, and they came back and said, ‘Oh, yeah, this guy can move, he’s going to be really good.’”

Was Marjanovic on board form the jump? “Hell yeah,” he said in an interview before the Sixers’ convincing playoff win Thursday night against the Toronto Raptors. “It was a new experience for me. The movies are amazing, great movies, everybody loves these movies. Movies that I’ve watched many times and then to get called to be a part of it is amazing.”

In the scene, Boban’s character is the first of what will be a hundred or so assassins who try to kill Wick, so it’s a small role but with a prominent position in the film. Reeves is the star, of course, and the outcome of the scene is never in doubt. Even so, Stahelski finds some (wait for it) novel ways to administer the final blow. The phrase “eat your words” comes to mind.

“He a super-nice guy. Very humble, and I remember he paid a lot of attention to detail. He really practiced his lines, and he got a lot of coaching from Keanu. This is like his first movie gig, and he’s quoting Dante’s Inferno, so it was a lot to ask. I give him credit, because that was a long day, and he really held up well and contributed.”

“Wow. This is a lot of compliments, he can move, big, tall, looks good,” Marjanovic said, laughing at his own joke, when he heard Staheleski’s review of his performance. “Perfect.”

It’s not unusual, Stahelski said, for Reeves to set aside time to help a guy like Marjanovic. Stahelski caught a big break working as Reeves’ stunt double in The Matrix (and its sequels). The two became friends, and Reeves encouraged Stahelski (and stunt partner David Leitch) in their ambition to become directors.

The two men got some work as second-unit directors on a couple of films (The Hunger Games, After Earth, Captain American: Civil War), and when the script for John Wick circulated, they expressed interest.

They got the job when Reeves essentially vouched for them. Stahelski said Reeves was also instrumental in helping them hold out for a decent budget — the first was made for less than $20 million, almost unheard of for a movie shot on location in New York City.

“We basically made that work by calling favors from everybody we knew, the best-trained people in the business,” he said.

Since then, the John Wick franchise has been a full-employment project for people in the stunt community — a chance for the professionals to ply their trade at a time when the industry relies more and more on computer-generated special effects in action sequences.

“I absolutely think that’s a big reason why people enjoy this series. In my mind, you’re more immersed in the story when you see the actual person doing the actual thing,” Stahelski said.

He and Leitch directed the first Wick together. Since then, each has struck out on his own. Leitch directed last year’s Deadpool 2. Stahelski is angling for a job directing a reboot of Highlander, the movie about immortal combatants, deadly only to each other, who duel down through the centuries.

“I just love the mythos of it, and the potential for world-building. And for somebody like me, this is the quintessential story. It’s an opportunity to take every fighting style from every culture for the last 1,000 years and integrate them, and construct a ballet around them. It’s not something you want to rush in to. It’s such a massive property, you want to make triple-sure you get it right.”

Sarah Todd contributed to this report.