You misunderstand. They both won't play at the same time. Few if any teams run a 2 back set these days. Parcells talked about not drafting/signing free agents to where you had more players at a position than you could get on the field. For example if you had drafted Tom Brady, Drew Brees, Aaron Rodgers and Peyton Manning it would be a bad draft because you couldn't play them all at once. As opposed to having Fitz, Jerry Rice, Calvin Johnson and Q who you could get on the field at the same time.
I feel better because I have a new favorite player. The Big Prez.
However, what I don't understand is that the Cards had 9 draft picks. I criticize one of them and a 1000 people get their panties in a wad. Do you guys go home at night and mainline Cardinal Kool-Aid.