Howard was earlier skeptical about casting Hemsworth as Formula One racer James Hunt but changed his mind later.
"It was uncanny. Chris is a surfer and although James wasn’t a surfer, he projected a kind of California cool," Howard said in a statement.
"There was something about the way Chris carried himself and his body language and even what he was able to do preparing his own audition just based on watching an interview with James that was really exciting," he added.
"Rush" is based on the rivalry between James Hunt and Niki Lauda in 1970. Actor Daniel Bruhl will play the role of Lauda. The movie will release Sep 20.
Birthday special: 14 Bollywood actors who made it big on TV
Photos: Vaani Kapoor, Poonam Pandey, Sana Khan at fashion event
Photos: Rishi Kapoor, wife Neetu, daughter Riddhima at book launch
Photos: Sunny Leone, Shraddha Kapoor, Shriya Saran at Mumbai airport
How Angelic! 10 stunning pics of birthday girl Angelique Kerber