If Dallas can't afford to resign Murray in addition to Dez then no way can they afford to sign Petterson, they're already going to be relatively high on the cap space scale before they've resigned anyone(137 million tied up going into next year). This will only leave them with an estimated 5-8 million in free cap space and even with the Cowboys being pretty good at working with the cap Dez is going to command top WR dollars which these days seems to be in the 15+ million a year range, which means they'll have to seriously rework some contracts and even cut some just to afford Dez and pay they're draft picks. Top tier RBs meanwhile average 7-9 million a year, and Petterson shatters that average right now by making 14 million a year on his last contract.