There was a time when it didn’t look like Tyrann Mathieu would play in the National Football League.

Despite being named the SEC Defensive Player of the Year and finishing fifth in the Heisman Trophy balloting in 2011, off-field troubles derailed Mathieu’s LSU career and put his pro prospects very much in doubt.

Those issues are in the rookie’s rearview mirror as he and his Arizona Cardinals teammates get ready for their season opener Sunday in St. Louis. But Mathieu isn’t overwhelmed by the enormity of his first real NFL game.

“I can’t say that I really have butterflies, man,” Mathieu said Friday. “I’m just excited to finally have the opportunity to play in my first career NFL game. It’s blessing, I’m humbled and I just want to go out there and do what I do.”

Mathieu played well in Arizona’s preseason games, registering 12 total tackles and a quarterback sack. He also averaged 7.7 yards on three punt returns.

Because of his solid preseason, Mathieu feels comfortable heading into live fire for the first time.

“I feel like I’m an NFL player, I’ve been practicing like an NFL player,” he said. “I think my understanding of the defense and what we’re trying to do is getting better every week and I’m just looking forward to going up against some opponents for four quarters.”

One of the opponents Mathieu will face Sunday is a familiar one. Rams’ rookie wide receiver Tavon Austin should be a focal point of the St. Louis offense Sunday, and the “Honey Badger” is familiar with his game having faced him twice in college while Austin was at West Virginia.

“He’s a great talent, we’ve got a ton of respect for each other,” he said. “We definitely like competing against each other and challenging each other.”

LSU beat West Virginia in 2010 and 2011, with Mathieu collecting an interception in each game. But Austin did have a huge game in 2011, catching 11 balls for 187 yards in a game LSU won 47-21.

“He’s quick, you can’t give him a lot of space — he’s definitely going to make the most out of it,” Mathieu said. “But I think you challenge him at the line of scrimmage and just compete with him for four quarters, I think it would be good for me.”

Opposition aside, Mathieu has a goal for his first game and beyond.

“Hopefully I’m exciting, hopefully I’m entertaining and hopefully I’m doing my job to the best of my ability.”

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