New reports have emerged saying that Jake Gyllenhaal has gained 15 pounds of muscle in preparation for his role as a champion prize fighter in the upcoming 2015 film 'Southpaw'.

The Weinstein Company released their first image of Gyllenhaal in 'Southpaw', showing the actor's physical transformation in order to play the role of Junior Middleweight Champion Billy "The Great" Hope. Hope is a left-handed champion boxer who tried to fight his way to the top after his career and his life faced a downfall following a personal tragedy.

During an interview with the film's director Antoine Fuqua, he told Deadline that he was excited for Gyllenhaal's transformation. He shared that the actor trained in the ring twice a day for seven days a week in order to build his physique, and that the both of them went to see the matched of boxers such as Floyd Mayweather and Manny Pacquiao for inspiration.

"Jake, my God, he's a very electric, powerful fighter in this movie," Fuqua said, "I'm confident that this will change how people see Jake."

This is not the first time Gyllenhaal endured a drastic physical transformation for a role, as he recently lost 25 pounds for the film 'Nightcrawler' before starting his training for 'Southpaw'.

Fuqua even admitted that it was Gyllenhaal's dedication to the role that might have resulted in his separation with then-girlfriend Alyssa Miller, as the actor spent most of his time at the gym training and sparring.

"No one but fighters understand the sacrifice it takes to be a fighter," the director said.

'Southpaw' is set for release in 2015. It is directed by Fuqua and written by Kurt Sutter. It stars Gyllenhaal as Hope, Naomie Harris as Angela Rivera, Rachel McAdams as Maureen Hope, Victor Ortiz as Ramon, Forest Whitaker as Titus Wills and more. It also stars rapper 50 Cent, singer Rita Ora and actor Tyrese Gibson.