Patrick Peterson's impact in Arizona

The moment the Cardinals added Patrick Peterson, their secondary vastly improved. Jerry Lai/US Presswire

In attempting to implement a turnaround for a defense that allowed the third most points and fourth most yards in the league last season, Arizona head coach Ken Whisenhunt may have borrowed a page from Bill Walsh's defense-building playbook. And in the process, he may have reshaped a porous defensive unit into an elite one almost overnight.