"Creed," starring Stallone and Michael B. Jordan as the title character, opened in theaters on Wednesday and received a warm reception from critics and box office audiences.
The cast -– Stallone, Jordan and Tessa Thompson -- chatted with ABC News’ Sara Haines about the project.
Jordan plays Adonis Creed, the son of the late Apollo Creed, who was Rocky's friend and former rival. Stallone plays Adonis Creed's mentor, boxing trainer and father figure.
Jordan said he had a chance to "fall in love" with the franchise as he prepared for this role.
"When you watch it back to back to back to back ... and see him," Jordan said, pointing at Stallone -- "literally age in front of my eyes. Kind of cool."
Thompson plays the younger Creed's love interest and an up-and-coming singer. She said Stallone had "a wealth of incredible stories" to tell his cast mates, especially in answer to their questions about what it was like to make the earlier films in the franchise.
"It was fun," Stallone said of those discussions.
When Haines asked whether there was any competition between the old and new guard, Stallone replied, "No," while Jordan laughing said, "Oh yes."
"Oh yes it is! If we put some gloves out here right now and a bag, it would definitely be a competition between the two of us," Jordan said.
"I will say this," Stallone put in. "(Jordan) trained much harder than I thought humanly possible ... He's in there with a real pro that can break bones on every punch. And I saw it. It was no joke."