The Arizona Cardinals have confirmed that Tyrann Mathieu will start the team's pre-season game against the Dallas Cowboys later this week.

The rookie free safety will replace Rashad Johnson, who sustained knee and ankle sprains during practice earlier this week.

The 21-year-old told the Cardinals' official website: "I couldn't fathom it. It was probably a long shot. I'm just putting in hard work, man, and things are finally starting to come together for me.

"You just go out and make plays. I don't think there's any science to it. Physical characteristics will play its part in certain situations but for the most part, it's all about making plays and being in the right spot at the right time. It seems everyone is starting to root for me again, which is definitely encouraging

"It just gives me an opportunity to go help my team. Of course I wish Rashad a speedy recovery because he was one of those guys who showed me the ropes from a safety standpoint. But it gives me the opportunity to go out there and be there for my teammates."

Mathieu, who was suspended for his final college season for breaching team rules, took his first sack during his NFL debut against the Green Bay Packers last week.