T.R. Knight, who is best known for playing Dr. George O'Malley on the ABC medical drama Grey's Anatomy, has joined the cast of the feature film 42, which is based on the life of Jackie Robinson.

According to The Hollywood Reporter, Chadwick Boseman will play Robinson, the legendary baseball player who in 1947 broke Major League Baseballs' color barrier.

Knight will portray Harold Parrott, the Dodgers traveling secretary.

The 39-year-old Knight left Grey's Anatomy in 2009, several years after Knight and co-star Isaiah Washington were involved in an altercation in which Washington hurled a gay slur at Knight.

The incident made headlines and shortly thereafter Knight publicly acknowledged he's gay.

“I guess there have been a few questions about my sexuality, and I'd like to quiet any unnecessary rumors that may be out there,” Knight said in a 2006 statement. “While I prefer to keep my personal life private, I hope the fact that I'm gay isn't the most interesting part of me.”

Knight guest starred last season on Law & Order: SUV.