Sylvester Stallone feels "fortunate" to have been a part of Carl Weathers' life.

The actor starred as Apollo Creed in the 'Rocky' film franchise, and his former co-star has taken to social media to pay tribute to Weathers, after he passed away aged 76.

In a video message posted on Instagram, Stallone said: "Hello everyone, today is an incredibly sad day for me. I'm so torn up I can't even tell you. I'm just trying to hold it in because ... Carl Weathers was such an integral part of my life, my success, everything about it.

"I give him incredible credit and kudos because ... when he walked into that room and I saw him for the first time, I saw greatness. But I didn't realise how great. I never could've accomplished what we did with 'Rocky' without him."

Stallone, 77, still has fond and vivid memories of filming the 'Rocky' movies with the Hollywood star.

And the veteran actor has admitted to being devastated by the news.

Standing in front of a painting inspired by the 'Rocky' movies, Stallone added: "He was absolutely brilliant. His voice, his size, his power, his athletic ability. But more importantly, his heart, his soul.

"It's ... it's ... a horrible loss. And I'm standing here in front of this painting because it was probably the last moment we were ever in the ring together and I'll never forget it. He was magic and I was so fortunate to be part of his life. So, Apollo, keep punching."

Stallone captioned his Instagram post: "We lost a legend yesterday. My life was forever changed for the better the day I met Carl Weathers. Rest in power and keeping punching."