After taking reps with the starters during offseason practices, Mathieu appears ticketed for nickel packages with a chance to claim the free safety job.
Asked Wednesday by Steve Wyche of NFL Network's "NFL AM" if Mathieu could step right in and make an immediate impact, coach Bruce Arians replied, "I don't think there's any doubt. ... He's getting his hands on a lot of balls. The guy's got amazing instincts and closing speed."