The Cardinals’ official depth chart this week confirmed the obvious: rookie Tyrann Mathieu is now starting in place of Rashad Johnson at free safety. Johnson missed two games and was limited in a couple of others after suffering a severed fingertip against the Saints. He was healthy enough to start two weeks ago against the Falcons, yet it was Mathieu at safety in the base defense. Johnson declined comment on the change but did say he is healthy. “I don’t think I’m limited at all,” he said. “I think my play speaks for that.” Johnson played in nickel situations against the Falcons, with Mathieu moving to play the third cornerback spot. Johnson intercepted two passes, and Mathieu had seven tackles, one interception and two passes defensed. “He (Mathieu) gives us a little bit more versatility as far as playing man coverage with the tight ends we face and the receivers we face,” defensive coordinator Todd Bowles said. “It’s kind of like having three quasi-corners out there, if you must. And he’s still a good tackler as a safety and he has great ball skills and great hand coordination. “Nothing against Rashad. Rashad’s a damn good safety and he’ll play a ton, too.” Mathieu and Johnson have a good relationship, and Johnson continues to provide help, Mathieu said. “He’s a pro,” Mathieu said of Johnson. “He comes to work every day with a smile on his face. He makes sure he still coaches me and helps me along the way. I don’t see any difference in him.” Mathieu will continue to start in the base defense and then move to cover a slot receiver in nickel situations. Johnson enters the game then at safety. Against the Falcons, Mathieu missed only one snap on defense, while Johnson played on 63 percent of the snaps. That probably will be the ratio going forward, depending upon the opponent.