Defensive back Tyrann Mathieu is a changed man. At least, that's what the former Heisman Trophy finalist wants NFL teams to believe. So when Mathieu arrived at the combine this weekend, he was less worried about excelling on the football field and much more intent on convincing coaches and GMs that he won't be a problem child if and when he arrives at the next level.

Following a turbulent 2012 that saw him dismissed from the LSU football team during the summer for failing a drug test and later arrested in October for marijuana possession, Mathieu realizes he almost completely squandered a chance to better his life through football.

Undoubtedly, his off-the-field troubles last year cast him as a troubled kid who is immature at best and self-absorbed and deeply irresponsible at worst. Mathieu realizes his fall from grace cost him a lot.

"Millions," he said Sunday at the NFL Combine in Indianapolis. "But at the end of the day, I'm not focused on money right now. I just want to start playing football again because my whole life I've been playing for free. So to play for a couple hundred thousand dollars, it's still football to me."

So now comes the test for NFL teams aiming to determine whether investing in Mathieu is misguided. If you need a detailed look into why teams might be scared away, visit this Sports Illustrated story from last fall, which not only delivers details of Mathieu's father being imprisoned as a convicted murderer when he was a toddler but also reveals the trappings of the social circles Mathieu found himself in.

Here's a short excerpt:

Late in high school Tyrann and his friends formed a crew called Era Nation, made up of a dozen self-described athletes, rappers and songwriters. Era Nation remained part of Mathieu's life after he moved to LSU, and he stayed tight with the group even as he became nationally famous. Mathieu felt so strongly about Era Nation that Era was part of the handle on his Twitter account (@TM7_Era), which he recently shut down.

Over the last year Mathieu has appeared with his Era Nation buddies in multiple videos online that show them at clubs partying. In another video Mathieu wears a shirt that says, HERE'S TO FEELIN' GOOD ALL THE TIME. One Era Nation member who appears in many of the videos with Mathieu, Samuel Brooks, a rapper who goes by the name of Yung Soop, told SI about Mathieu's marijuana use: "It was a recreational thing. I don't believe he's addicted." Brooks, who was arrested in December 2010 for battery against his mother and later pleaded guilty to a charge of criminal damage, has also tweeted about producing Honey Badger T-shirts. Cordova says that Era Nation has been using Mathieu's celebrity to advance its own agenda. "When Tyrann started doing well, Brooks went around telling people, 'I don't have to do nothing now,' " Cordova says. " 'Tyrann's going to put me on when he goes to the league.' "

And that story was published before Mathieu's October arrest.

But now Mathieu is trying to clean up his life. He said Sunday that he has changed his outlook on things and tried to surround himself with support from guys who have made it to the NFL. That includes former LSU teammates Morris Claiborne and Patrick Peterson as well as Darelle Revis and Corey Webster.

Furthermore, with NFL teams in tune with every misstep in his past, Mathieu is facing his issues head on and trying to be as straightforward as possible with all he's been through and learned in the past year.

"My best friend right now is honesty. I want to be as open as possible. Because I'm trying to rebuild my trust."

Mathieu said Sunday that being kicked off the LSU team initially felt like rock bottom. But then came that October arrest.

"That's a different bottom," he said. "So I decided to go to rehab. But this time the rehab was for Tyrann. I just wasn't going to it for publicity or because my school told me to go to it. I wanted to get my problem corrected."

Mathieu shrugs and laughs off the notion that his 5-foot-9-inch height will hinder him from succeeding at the next level.

"They can watch a whole lot of film on me," he said. "I make plays. Height has very little to do with playing the game of football."

Bigger questions will center around Mathieu's drug issues and overall maturity. If he was unable to stay clean even after getting thrown off the LSU team, who's to say temptation won't swallow Mathieu again when he gets to the pros and increased money and attention come pouring in?

"Because I've been through it," Mathieu responded. "I know what it's like not to have football. I know what it's like not to be in the front of the room, not to be the center of attention. And I know what it's like to be humiliated. And to go back down the road? Nah. Not a chance in this world. Not a chance in my lifetime again.

"But everything is a process. I'm not saying that I'm totally there. But I am taking strides every day to be the best person that Tyrann can be."