No. Brett Ratner wanted an unknown, he found an actor in Matthew Boomer, but WB did not want an unknown. McG looked through many established and unknowns and hadn't yet decided before he was let go of the project. It was the indecisiveness between the director and the studio that kept an actor from being cast. People forget that when Singer came onboard WB came him cart blanche basically. And Routh was so easily chosen because he was a candidate for McG, and Singer reviewed all the actors that the previous directors auditioned. WB gave him the creative control that he didn't get on the X-Men movies and that WB didn't give Ratner or McG, which is partially why Singer jumped ship so damn quickly (the deal for Singer to direct was made in 72 hours).
You're right Ratner also wanted an unknown. But, like I said, if you have a director and producers with a clear idea of what they're looking for in an actor (and backing from the studio) then finding one doesn't have to be a huge, long ordeal. Obviously that's a big "if", but such is filmmaking.