The Rocky star was asked if he had been in touch with Willis since his family announced in March that he was retiring from acting after being diagnosed with aphasia, a cognitive disorder that affects a person’s ability to speak and understand others.
"Bruce is going through some really, really difficult times," Stallone told The Hollywood Reporter. "So he's been sort of incommunicado."
He went on to say, "That kills me. It's so sad."
The pair have been friends for years — as well as business partners. In the early '90s, they banded together — along with Arnold Schwarzenegger and Willis's first wife Demi Moore — to back the Planet Hollywood franchise.
They went on to co-star together in Stallone's The Expendables franchise, which earned big bucks at the box office. However, while negotiating a deal for the third film in 2013, they had a spat over Willis's salary. Willis reportedly wanted $4 million for four days of filming while Stallone wouldn't go above $3 million. Stallone blasted Willis as "greedy and lazy" on social media. While Willis stopped playing Mr. Church, they did make up, with Stallone later clarifying that Willis was "a stand-up guy." At the press conference ahead of the film's release, Stallone said calling Willis out was "nothing personal."
When the Willis family shared the news about his health earlier this year, Stallone was one of the Hollywood stars to react publicly. On social media, he posted a series of old photos of them together, writing,"We go back a long way, praying for the best for you and your wonderful family…"
Since Willis's retirement, he's kept out of the spotlight with the only real updates coming from his wife, Emma Heming, and his family. One of the last ones was a sweet video, set to Maren Morris's "The Bones," showing highlights from their summer. Willis danced with his two youngest daughters, gave one a piggyback, played frisbee and kissed his wife, among other sweet moments.
Willis has a few completed films in the hopper, including Paradise City, out Friday, which reunites him with his Pulp Fiction co-star John Travolta. According to a New York Times review, Willis "appears relatively alert and aware," despite reports of his struggles on the set before the diagnosis. It did note that Willis had little screen time and his one scene with Travolta "was clearly achieved through editing." He actually didn't share a frame with his other co-stars, and "more than once it sounds as if his dialogue was dubbed in by a similar-sounding actor."