On Movies by Steven Rea

If you thought Jake Gyllenhaal's transformation for last year's Nightcrawler was extreme - losing weight and gaining a creepy intensity to play a feral freelance video cameraman trolling the streets of L.A. - look at the actor in Southpaw.

You may not recognize the man.

As Billy "The Great" Hope, a pro boxer who grew up in a Hell's Kitchen foster home and now owns the title of light-heavyweight champion of the world, 34-year-old Gyllenhaal is all muscle, sinew, tattoos, bling. He's a prizefighter who prides himself on the punishment he can take in the ring - before he delivers the final blows to his opponents. Billy's record? 43 and 0. And to see Gyllenhaal in Southpaw, which opens Friday, is to believe it.

Harvey Weinstein, whose eponymous company is distributing the Antoine Fuqua-directed drama, has declared that this is the role that will win Gyllenhaal his Oscar. While hyperbole is typical of the veteran showman, he may have to be taken seriously this time around. Gyllenhaal trained six hours a day, seven days a week for six months, running, jumping, weightlifting, and sparring under the tutelage of former boxer Terry Claybon.

"I was a Mike Tyson fan as a kid - it's kind of hard not to be when you grew up in the '90s," Gyllenhaal says. "But I was a man who knew very little about boxing. . . . And I knew that to pull it off, I was going to have to learn how to do it."

In Southpaw, Gyllenhaal's Billy is living the life: a mansion in the 'burbs, a beautiful wife (Rachel McAdams), a daughter (Oona Laurence) who loves him, a posse of friends - including his longtime manager, played by Curtis "50 Cent" Jackson - at his side. Billy's bouts have earned him millions, but to assuage his wife's fears that he's damaging his body, and his brain, he agrees to a hiatus.

Then, one evening, it all collapses. His title, his family, his respect, his property, his bank accounts - gone. Southpaw, costarring Forest Whitaker as the neighborhood boxing-gym owner who trains Billy in his against-the-odds comeback try, is classic pugilist melodrama. Life is brutal. Punching somebody over 12 rounds in the ring? Brutal. Going to court to fight for custody of your child? Brutal.

"There are so many things that we've seen before in boxing movies," says Gyllenhaal, on the phone from Los Angeles last weekend and not even feeling the need to mention those movies by name. (We will: Rocky, Raging Bull, The Fighter, The Champ, Somebody Up There Likes Me, Body and Soul.)

"So, how do you make it seem original?" he asks. "For me, and for Antoine, the thing that's original about this movie is Billy Hope. It's who he is, and what he goes through, and what he experiences. A guy who's trying to get his life back together and learn how to become a dad and learn how to become a man. . . .

"That's what's at the heart of this movie: a guy who's been through the system, knows how it works, used his rage to beat the system, but ultimately, it's that same rage that destroys him. And he has to find his way back, learn how to grow up and do good."

Gyllenhaal says that he first met Fuqua, the director of Training Day and The Equalizer, a half-dozen years ago at one of "those Hollywood lunch meetings where somebody tells you how much they want to work with you, and you don't believe them."

So the actor, nominated for an Academy Award for his work opposite Heath Ledger in 2005's cowboy love story, Brokeback Mountain, went about his business - business that included some very fine work in End of Watch (2012) and Prisoners (2013).

"And then, about a year and a half ago, we met again about this project, and Antoine was like, 'I told you when we met last time there is something I see in you that I want to bring out.' And I was like, 'Really?' "

Really.

So, Gyllenhaal began his training - with Fuqua, who has boxed for years, right alongside him. And the actor came to appreciate what boxing was about.

"Obviously, it's a brutal sport," Gyllenhaal says. "But I also think it's a sport full of grace, and at the highest level . . . it's about an exchange of the minds."

Boxing, he says, is about "being alone in a space" - physical space, mental space - and for all its primal ferocity, it is a sport that involves science, geometry, speed.

"You have to be hyper-prepared and hyper-in-tune, and it is unlike really any other sport because it requires both offense and defense simultaneously."

Gyllenhaal has more than 30 credits on his CV now (his first was as Billy Crystal's kid in 1991's City Slickers). But when he looks over the films he has done, a few stand out - for the experience of making them, not for the success they may, or may not, have seen at the box office.

"Nightcrawler is one," he says of the drama written and directed by Dan Gilroy. "I'm really proud of that movie. Sometimes, when I think about it, I can't believe we pulled it off. We shot it for a very small budget in a very short time. . . . That's the kind of stuff that inspires me."

Jarhead, the 2005 combat drama based on Anthony Swofford's Marine Corps memoir, was "life-changing." Gyllenhaal puts Donnie Darko (the 2001 cult hit), Zodiac (David Fincher's 2007 serial-killer thriller), and Brokeback Mountain on his list, too.

The actor, whose sister is actress Maggie Gyllenhaal (Secretary, Crazy Heart) and whose parents are both in the business (Stephen Gyllenhaal a director, Naomi Foner a screenwriter), hasn't taken much of a break since shooting Southpaw.

He's got Everest, a mountain-climbing thriller, coming in September and At Risk, with Naomi Watts and Chris Cooper, scheduled for release in the spring. Gyllenhaal's about to start with director Tom Ford on an adaptation of the Austin Wright novel, Nocturnal Animals. And he and Fuqua have plans to reteam - outside the boxing ring - for The Man Who Made It Snow, about Max Mermelstein, the "Jewish street kid from Brooklyn" who would go on to serve as the American agent for the Colombian Medellin cocaine cartel.

A different kind of brutality altogether.

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