Five years ago, father-son producing partners Alan and Peter Riche surveyed the movie landscape and decided it was time for a boxing movie to be made.

The sweet science depicted on screen has always interested the two. Alan still remembers taking a much younger Peter to a repertory theater to see the classic 1931 movie “The Champ,” starring Wallace Beery as a washed-up alcoholic boxer who tries to turn his life around for the sake of his young son, played by Jackie Cooper.

“It’s a favorite of ours,” Alan told Business Insider, “and we decided to do our version of ‘The Champ.’”

Alan has been producing movies since the early 1970s, with credits over the years that include “Empire Records,” “The Family Man,” and the movie version of “Starsky & Hutch.” His son, Peter, has also had his own individual success, first as a talent-and-literary agent, followed by developing over 100 screenplays as VP of production for the company his father headed before the two teamed up to start their own.

"Southpaw" producers Peter, left, and Alan Riche. The Weinstein Company The Riches have been in the business long enough to know every project has its peaks and valleys, but getting a boxing movie they would call “Southpaw” off the ground turned out to be one of their most challenging yet.

Peter said the initial idea was “The Champ” meets “Raging Bull,” an authentic look at boxing but with a story that would be as gripping and raw as the action displayed in the ring.

Also, they needed to, as Peter put it, “flip it,” to make the story stand out from the classic boxing tales they were hoping to emulate.

He suggested to his father that instead of it being a father-son story, like “The Champ,” that it be about a father and his daughter.

Eminem. AP Photo/Matt Sayles But Peter also came up with an idea that would make Hollywood stand up and pay attention to the project.

Rapper Eminem should play the boxing father.

“We had both seen ‘8 Mile’ and loved it and thought he was really interesting and had a real presence on screen,” Alan recalled.

“I thought this guy hasn’t done a movie in a number of years, this might be interesting to him and, dare I say, a sequel to ‘8 Mile.’ Not literally in story, but a good fit for him,” Peter told BI. “We knew how important being a father to his daughter is. We didn’t fear going to Eminem and saying this is an amazing role for you and if you got yourself in shape it would be a tour-de-force.”

Perhaps the Riches could catch the reclusive rapper at the perfect moment. Though he came on for one episode to voice a character for the popular Comedy Central phone-pranking show “Crank Yankers” in 2004, and had a memorable cameo in Judd Apatow’s “Funny People” in 2009, Eminem hadn’t starred in a movie since 2002’s “8 Mile,” which was partially based on his life growing up on Detroit's impoverished 8 Mile Road in the mid-’90s. On the music side, he’d just released his seventh album, "Recovery" in June 2010, which debuted No.1 on the Billboard charts and was received well by critics.

Eminem in "8 Mile." YouTube / 8 Mile In October 2010, the duo pitched the idea to Eminem’s manager David Schiff, and, according to Alan, within 24 hours they heard back, with Schiff saying the rapper’s team wanted to do it.

The film would follow boxer Billy Hope, the reigning junior-middleweight-boxing champion, whose life is turned upside down following a horrific event that causes him to lose custody of his daughter and jeopardize his boxing career.

Once Eminem was on board, “Southpaw” was on the fast track. The Riches brought on “Sons of Anarchy” creator Kurt Sutter to write the script. And by December 2010, DreamWorks signed on to make the film. In June 2011, it was reported that Antoine Faqua ("Training Day") would direct.

“We knew Antoine boxes at least five days a week,” said Peter. “So we knew this person would make the boxing look authentic. He went out to Detroit and had a meeting with Eminem, and the feedback we got back from both camps couldn’t have been better,” Peter recalled. “Basically we were moving like a train to a green-lit movie.”

Director Antoine Fuqua. The Weinstein Company But according to the Riches, four weeks before Eminem was to begin training for the movie they got a phone call that the rapper no longer wanted to do it.

“We were told that he really loved it, but that he feels he’s a musician first and an actor second and he had a lot of inner energy going on for his next album and that’s where his muse was taking him,” said Alan.

Eminem would go on to make "The Marshall Mathers LP 2," which was released in 2013.

“That was the moment of pain,” Peter said after getting word Eminem was out. "That was the low moment.”

In a recent interview with Zane Lowe for Beats 1 Radio, Eminem said he “wouldn't have been able to do” “Southpaw” due to scheduling issues related to making the album.

With Eminem out, DreamWorks lost interest in the project. Thankfully, Fuqua still wanted to direct.

Following some talks with MGM to take the project, which Alan said “never got into negotiations,” Harvey Weinstein came calling.

“He had read the original script and very much wanted the project originally,” said Alan of the legendary producer who has been behind Best Picture Oscar-winners “Shakespeare in Love,” “The English Patient,” “Chicago," "The King’s Speech,” and “The Artist.”

The Weinstein Company bought the film rights in 2013, while the Riches continued looking for their Billy Hope.

Aaron Paul was considered for the role of Billy Hope in "Southpaw" after Eminem dropped out. John Sciulli/Getty Images for Tequila Don Julio “We talked at length with Aaron Paul,” said Alan. “Travis Fimmel from ‘Vikings,’ Charlie Hunnam from ‘Sons of Anarchy,’ but Harvey Weinstein always had it in his head that it would be Jake Gyllenhaal.”

Gyllenhaal had been on a stretch of taking on challenging and physically demanding roles, including 2012’s “End of Watch,” 2013’s “Prisoners,” and 2014’s “Nightcrawler,” in which he dropped 30 pounds to play a freelancer shooting gruesome accidents and crimes to sell to the local news stations.

When the Riches, Fuqua, and Sutter had a meeting with Gyllenhaal about coming on the film, he was still frail from the role and as Alan recalls, “was still in the head of that ‘Nightcrawler’ character.”

Jake Gyllenhaal in "Nightcrawler." Chuck Ziotnick/Open Road Films “To Antoine’s credit, he looked into Jake’s eyes and knew he could do the work with him,” said Peter.

Gyllenhaal trained twice a day for six hours, and gained the 30 pounds he lost for “Nightcrawler,” plus adding on 15 more for the role. Then during production, Peter said Fuqua and Gyllenhaal would work out every day before shooting.

Jake Gyllenhaal training for "Southpaw." YouTube/The Weinstein Company The Riches were taken aback by the actor's dedication, saying he gave the film everything he had every single day.

It shows on screen. Gyllenhaal's performance in “Southpaw” is as intense as the training he did, already leading to Oscar buzz for the actor.

He's even received praise from the original actor for the role. “Jake smashed it,” said Eminem in the interview with Lowe.

In fact, Eminem loves the movie so much he made two original songs for the film and is releasing the soundtrack on his label.

Looking back on the last five years, Alan and Peter don’t dwell on the struggle. (“We're doing ‘Tarzan’ for Warner Bros. and that’s taken 13 years to get made," said Alan.) But instead believe the experience has made the trust and love they have for one another even stronger.

“It had its challenges but it was worth every minute," Peter said about the film. “It was grueling but we would do it all over again tomorrow.”

“Southpaw” opens in theaters July 24.

Watch the trailer: