Reprising his role as Rocky Balboa in Creed earned Sylvester Stallone an Oscar nomination — but the industry nod comes as bittersweet praise for the actor, who lost his son, Sage, to a heart attack at 36 in 2012.

Creed, which is a tribute to Sage, is the story of how the indefatigable boxer Rocky becomes a father figure to the son of his late friend Apollo Creed, and the star tapped into his painful past for the role.

sylvester and sage stallone-getty images

Sylvester and Sage in 1990.

“Every time you can vent emotions that are real, I think that’s very helpful,” Sly, 69, tells Closer about his cathartic experience making the film. “Most importantly, I want to respect his memory. I think we did, so it was good.”

RELATED: CONGRATS! Sylvester Stallone Wins His First Golden Globe Award for Creed

Sly wasn’t sure he was emotionally equipped to take on the challenge when Sage suddenly passed away shortly after writer-director Ryan Coogler first approached him with the project. “It took a while,” he says. “I really didn’t want to do it — I swear to you. It’s just too painful. It’s rough. There is no closure. There is nothing. The wonderful thing about acting is that it’s a release. I can take some solace in that.”

To read the full story on Sylvester, pick up the new issue of Closer Weekly, on newsstands now!