Rookie the real deal for Cardinals

While difficulty in putting down the joint may be a bullet point you can't ignore in his profile, let's not forget about what type of football player Tyrann Mathieu is.

He's had his share of troubles with team conduct, as well as the law. Last August, Mathieu had been dismissed from LSU's football program for reported failing multiple drug tests. The following week, he attempted to get clean by entering rehab in Houston - only to find himself in more trouble later that October.

He and three former Louisiana State University teammates were arrested on marijuana possession charges. His teary-eyed, on-camera interview with ESPN later that fall indicated one thing: He was through. He wanted to get his life in order and play professional football.

He got right to work at the 2013 NFL Scouting Combine, tallying 4.5 seconds in the 40-yard dash, a 34-inch vertical and a 117-inch standing long jump. There's good reason why the Arizona Cardinals looked past his legal issues in drafting the former LSU standout with the 69th overall pick this past April. The dude can play. And given his Cardinals debut at St. Louis on Sunday, kudos to Arizona for giving him a chance. He will produce, without question. More importantly, he will be a major centerpiece in their defensive nucleus.

Arizona knew of Mathieu's potential dating back to his days in a Tigers uniform (when he was known as "Honey Badger").

At 5-foot-9, 192 pounds, Mathieu was a machine. He possessed great physical toughness and stability in LSU's secondary. The part that made him an even scarier adversary is his speed. While he's deemed a safety based on his physique, he could just as easily play cornerback. He's tough, hard-hitting, quick and instinctive.

Sunday's season opener gave the world another realistic glimpse of that.

With less than three minutes left in the first quarter, St. Louis Rams quarterback Sam Bradford found tight end Jared Cook on a quick strike up the middle. Just as Cook was about to cross into the end zone for the easy touchdown, Mathieu bolted toward Cook out of nowhere.

Mathieu saved what could have been a game-defining play, swoooping in with his right arm and, with an uppercut-like motion, forcing the ball out of Cook's arms. The Cardinals recovered in the end zone.

That one play did more than just keep it a tight ball game. It gave Arizona that much-needed confidence in the secondary. It gave them a strong sense of long-term reassurance in addressing the defense.

I know it's only the first game. But in terms of the bigger picture, those are the kind of moments Arizona needs for its defense to become dependable every game. They need someone who can succeed in all the dirty work. They need a guy who can really move and show no mercy in bringing opponents to the ground.

Mathieu did that in the marshlands of Baton Rouge, La. He can pick up where he left off with the Arizona Cardinals, and do so for a long time.