Sean Payton said that Larry (the guard at the time) would have to compete. That player was cut/released later that offseason. I could be wrong but I believe Payton said the plan was to move McCoy to guard at first and then McCoy was too good at center to justify the move whilst Ruiz was good enough at guard (Keep in mind we still had Drew Brees making all the calls and adjustments), so they kept McCoy at center and went with Ruiz on his right.