Cillian Murphy’s sacrifice for ‘Oppenheimer’ isn’t being overlooked by Robert Downey Jr.

Cillian Murphy‘s performance in Oppenheimer has been wildly praised by fans and critics alike, and it shouldn’t be overlooked. While people were impressed by how he portrayed J. Robert Oppenheimer, his co-stars recognized the weight of the task given to him when he was cast to play the lead in Christopher Nolan‘s latest blockbuster.

It was mentioned in the past that Murphy had to do plenty of reading in preparation for the role. But that’s nothing compared to what his co-star, Robert Downey Jr. said during his interview with People Magazine.

He claimed that Murphy spent his free time practicing and learning different skills to execute playing the “Father of the Atomic Bomb” to Nolan’s standards. This meant that he couldn’t engage in other activities with his fellow co-stars between scenes, which made sense since he had to be able to speak another language fluently, or confidently convey that he had thorough knowledge of scientific concepts what he was talking about.

“He knew it was going to be a behemoth ask when Chris called him. But I think he also had the humility that is required to survive playing a role like this.

“We’d be like, ‘Hey, we got a three-day weekend. Maybe we’ll go antiquing in Santa Fe. What are you going to do?’ ‘Oh, I have to learn 30,000 words of Dutch. Have a nice time.’ But that’s the nature of the ask.”

Downey Jr. commented on Murphy’s dedication as a “greater sacrifice,” something that he hadn’t seen throughout his 53 years working in the industry.

“I have never witnessed a greater sacrifice by a lead actor in my career.”

It’s no doubt that all that work has finally paid off. Early reactions to the film praised the cast’s performance in what some describe as a “dense” biopic. Murphy’s acting chops in particular have Nolan wanting the star to play him in a biopic about his life, should such a project ever materialize.

Oppenheimer currently enjoys a certified fresh rating of 94 percent on Rotten Tomatoes and earned $80.5 million during its domestic opening. If you want to see whether Murphy’s performance matches up to his co-star’s praise, Oppenheimer is now showing in theaters.