Robert Downey Jr. is opening up about what is arguably his biggest role to date – playing Iron Man in the Marvel Cinematic Universe.

The 58-year-old actor made his debut as the billionaire Tony Stark in 2008′s Iron Man, and he bowed out over a decade later with 2019′s Avengers: Endgame.

During a new interview, Robert admitted to having some concerns about spending so long in the role. He also opened up about some of the choices he was making immediately after leaving the franchise, revealing another concern that he had but ignored.

Read more about Robert Downey Jr.’s Marvel experience…

Robert told The New York Times Magazine that he “A hundred percent” had concerns about spending so much time as Iron Man. He continued, reflecting on his latest movie – Christopher Nolan‘s Oppenheimer. “I knew there was a point where Chris Nolan was endorsing, let’s work those other muscles, but let’s do it while rendering you devoid of your usual go-to things.”

Before he could join the cast of Oppenheimer, though, Robert signed on for another franchise. However, it wasn’t anywhere near as successful as the MCU.

“I finished the Marvel contract and then hastily went into what had all the promise of being another big, fun, well-executed potential franchise in Dolittle,” he recalled (via People).

As it turns out, there were concerns there, too. “I had some reservations. Me and my team seemed a little too excited about the deal and not quite excited enough about the merits of the execution,” he admitted. “But at that point I was bulletproof. I was the guru of all genre movies.”

If you missed it, Robert recently revealed the “best film [he's] ever been in.” He’s also previously revealed if fans will see him in the MCU again.

Did you know that another A-list actor was rumored to be playing Iron Man before Robert landed the part? Find out what he had to say about the whispers over a decade alter.