I think [Creed director/co-writer] Ryan Coogler was really interested in authenticity, and had thought that maybe Bianca would be played by a musician that was maybe making her acting debut. Then I think what he found is that he wanted to make sure that whoever played Bianca could really challenge Mike, both as a character and an actor. So I think at that point it made sense to have an actor step into the role. [Ryan and I] had met at Sundance when I was there with Dear White People and he was there actually just taking a break from writing Creed to just see some movies. I think it was helpful for him to know that I had been onstage, that I could be onstage. He didn’t know much about my writing specifically, but I think he felt pretty safe once he knew that I could be onstage and command that part.
Behind the scenes vid:
"If it were UFC you could pull his hair."
A ton more pics and quotes @ the source