If you’re looking for someone to throw a punch or take on a zombie horde, well, Jon Bernthal’s probably your guy. But when you’re looking for an actor who can credibly serve-and-volley, he might not spring to mind.

That was the dilemma facing “King Richard” director Reinaldo Marcus Green when he was looking for someone to portray Rick Macci, the tennis coach who took a chance on a young Venus and Serena Williams. Bernthal has made a career playing tough guys, such as gritty Marvel antihero Frank Castle or “The Walking Dead’s” Shane Walsh. When looking for an actor to play Tony Soprano’s father for “The Many Saints of Newark,” Bernthal, who has broken his nose more than a dozen times, made perfect sense. But to play the happily square Macci, he wasn’t an obvious fit. Imagine casting the Punisher as Ned Flanders.

“He rolled up to our meeting wearing a hoodie and his sweatpants high above his ripped waistline, his pit bull, Bam Bam, riding in the front seat of his car,” Green recalls of their first encounter. “He looked nothing like Rick Macci.”

But Bernthal loved the script and its message. The film centers on Richard Williams (played by Will Smith) and his determination to teach his daughters not only the sport of tennis but the business, as they break into an exclusive world. While the elder Williams ruffled feathers — his battles with Macci are some of the film’s best scenes — his love for his family is never in doubt.

“It was this meditation on family and fatherhood,” says Bernthal. “My kids are the absolute center of my life, and raising them with discipline and responsibility and teaching them kindness and empathy and rigor are all things I take enormously seriously.” Bernthal even auditioned, putting himself on tape.

But meeting Green sealed the deal. The two began speaking about their passion projects, growing up athletes and their own children. Then Bernthal told the director he had already started losing weight for the role. “His goal was to lose 30 pounds,” Green recalls. “I don’t know where he could find 30 pounds because he was shredded. But I was blown away by his commitment.”

And while Macci might not be as bombastic as Bernthal’s other roles, that doesn’t make him any less strong. “I think there’s sort of this confusion now and false representation about what masculinity is and what toughness is,” Bernthal notes. “Oftentimes, it’s all about being the loudest voice in the room, and that, to me, doesn’t necessarily mean tough. I think compassion, intellect, empathy and kindness are also huge staples of masculinity. Rick is every bit as tough, just in a different way. His mask is a mask of joy, and that is an enormously powerful and strong thing.”

Though Bernthal has portrayed characters based on real people before — most recently Lee Iacocca in “Ford v Ferrari” — Macci was unusual in that the actor was actually able to speak to his real-life counterpart. “We talked on the phone, and I spoke to a lot of people who played [tennis] under him,” says Bernthal. “And I talked to Serena, who described her time with Rick as some of the most fun times of her life.”

A critical part of his preparation was learning the sport. Though athletic — Bernthal played football in high school and baseball for a professional Russian team, and has a boxing background — he knew little about tennis.

“If you’re playing a soldier, you have to know the weapons. If you’re a math teacher, you better understand the concepts,” Bernthal reasons. “I had to learn the vocabulary of the world and get the tennis right.” He trained extensively and even coached a 16-year-old player named Kamea Medora (Bernthal called her “the Champ”). Now the actor is hooked. “It’s one of the huge privileges “of doing this for a living. You get to learn these new skills,” he says. “I’d never played before, and now I play all the time. I love it.”

Green is thrilled Bernthal convinced him to go against his initial casting instincts. “Jon is the guy you want with you in the trenches, in the mud,” Green raves. “He is a roll-your-sleeves-up, hard-nosed, fearless actor.” Green adds that Bernthal more than held his own improvising with Smith, and formed a real bond with Saniyya Sidney and Demi Singleton, who play Venus and Serena. Now, Green and Bernthal are collaborating on the upcoming HBO limited series “We Own This City,” from “The Wire” creator David Simon and producer George Pelecanos.

It’s one of many projects on the actor’s busy slate. In addition to “The Many Saints of Newark,” he can currently be seen in B.J. Novak’s anthology show “The Premise” and in the film “Small Engine Repair.” The latter is an adaptation of John Pollono’s play that tackles issues of gender head-on. Bernthal performed onstage to great acclaim in Los Angeles in 2011 and then Off Broadway in 2013.

Pollono has nothing but raves for his collaborator; he says Bern­thal always wanted to turn the play into a film. “I remember Jon driving me to get a taco before a show. We were eating in his old beat-up F-150, and he said something like ‘We gotta keep making shit together,’” recalls Pollono. “It was like a romantic comedy: I wanted to say it first but was afraid to, and was almost speechless when he said it.”

And Bernthal kept his word, returning to do the show Off-Broadway after breaking through in “The Walking Dead.” “I was wor­­ried that since his career was taking off, he’d forget about our partnership,” says Pollono. “A lot of people are ‘set friends’ and disappear when the show is over. But J.B. isn’t that guy. He says what he means. And here we are 10 years later and still collaborating.”

Bernthal is also becoming more involved as a producer; in addition to “Small Engine Repair,” he is an EP on the upcoming Lena Dunham film “Sharp Stick,” in which he appears.

Up next is a role in “The Unforgivable” as Blake, co-worker and love interest of Sandra Bullock’s character, a recent parolee. Unlike “King Richard,” there was no hard sell required. In fact, Bullock asked him to take the part. Actually, she pleaded. “Calling Jon and begging him to do this — and he didn’t want to do it at first — was easy for me to do,” Bullock tells Variety. “No one else would have worked. There is something about Jon that feels 1,000% authentic. There isn’t a facade or a style that he is putting on to sell a brand. No one else could have come to that specific character and made it feel like a real human being.”

Echoes director Nora Fingscheidt, “I knew Jon mostly from his roles as a tough guy, but he also has such a warmth and incredible honesty to him that it was clear after the first meeting he is the perfect cast. Blake is the one person that makes our main character Ruth open up and we needed somebody who can pull this off, while avoiding all clichés.”

On the end of the spectrum, Bernthal will star in a reboot of “American Gigolo” for Showtime, sliding into the role Richard Gere played in the 1980 film. “When you see me with my giant ears and my big nose, you can tell it’s gonna be a little bit different than that,” he jokes. “Look, it scares the shit out of me — and ultimately that’s 100% why I decided to walk towards it.”