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By now, we all know about Arizona Cardinals third-round pick Tyrann Mathieu and his backstory. Prior to being drafted this past April, Mathieu tarnished a promising collegiate career with drugs and other off-the-field incidents.

Which, in turn, hurt his overall stock. Some felt the All-American defensive back could have been a Day 1 pick with a solid junior season. Here’s what NFL draft analyst Mike Detillier had to say about Mathieu before his third season at LSU, via Josh Weinfuss of USA Football:

Barring any sort of injury, he’s going to be a first-round pick in the NFL, and he’s going to play a long time, because you can’t coach what he has, just natural football instincts around the ball.

Unfortunately, Mathieu’s off-the-field headaches forced him to miss the entire 2012 season. Yet that year away from the game hasn’t hurt his ability, nor the way he plays. He still has incredible instincts. He makes a ton of splash plays and is marvelous at taking the ball away.

Even though Mathieu has only played in two preseason games, he has already established himself as an impact player on defensive coordinator Todd Bowles’ defense. In 74 defensive snaps, the ball-hawking athlete has tallied 11 total tackles, one quarterback sack and one pass defended.

However, statistics can only tell a part of the story. Let’s go to the tape and analyze why Mathieu will be critical to Arizona’s defensive success.

The one attribute that attracted the Cardinals to Mathieu was his versatility in the defensive backfield. He can play either safety (of the free variety) or cornerback (in the slot).

Arizona has already used him at each position during both of its preseason games.

On this play against the Packers, Mathieu lined up as the slot cornerback on the left side of the defensive formation. Green Bay deployed a "11" personnel (three wide receivers, one tight end and one running back) look.

Quarterback Graham Harrell was either looking to hit the tight end or the slot receiver on a "9" route. From the get-go, Mathieu wasn’t worried about covering the slot wideout. His main objective was to get into the quarterback's head. He did this by coming up to the line of scrimmage and faking the blitz.

After he faked the blitz, he retreated back to his original position over the receiver. Once the ball was snapped, Mathieu was in hot pursuit of the quarterback. Yet he wasn’t the only one aiming to take down Harrell.

In addition to Mathieu, Bowles sent two linebackers and two defensive linemen.

Harrell thought Mathieu was bluffing the blitz, so he went ahead with the called protection scheme. His failure to recognize the blitz and adjust the blocking scheme accordingly left him dead in the water.

By the time Mathieu got to Harrell, no one was open. Linebacker Colin Parker (No. 52) had the tight end well covered, and strong safety Jonathon Amaya (No. 27) picked up the slot receiver. Bowles drew the play up perfectly, and his defense executed.

This next play didn’t result in a sack like the first one, but it did show pundits that Mathieu is a sound tackler who does a nice job against the run.

Under the direction of quarterback Tony Romo, the Cowboys offense was also in 11 personnel. Arizona’s defense matched Dallas’ grouping with a run blitz out of the 3-3-5. Mathieu lined up in the slot on the right side of the formation, over wide receiver Miles Austin.

After the snap, Romo handed off to running back DeMarco Murray on a strong-side stretch run. Instead of immediately engaging Austin, Mathieu took a step back and opened up his stance, since he identified the play as a run.

With a clear path to the ball-carrier, Mathieu did a phenomenal job of squaring up his shoulders. His perfect positioning allowed for an easy stop for no gain. If he hadn't acknowledged that the play was a run right away, Murray likely would have run for a first down and kept the drive alive.

The last play zeroes in on Mathieu’s strong understanding of how to excel in pass coverage.

Mathieu was covering slot wide receiver Dwayne Harris (No. 17). Harris was looking to run a slant pattern to the first-down marker over the middle of the field. As it was third down, Mathieu was in tight press coverage.

He secured an acceptable jam off the line of scrimmage, which coincidentally took Harris right out of the play. Without question, quarterback Kyle Orton was looking over the middle of the field, but there was nothing there to be had.

Aside from the ridiculously tight coverage, Mathieu did a great job reading Orton’s eyes during the play. His stout, physical presence took away one option and forced Orton to throw to his only other option (tight end James Hanna).

Orton’s read was okay, but Hanna’s route was sloppy, and cornerback Jerraud Powers jumped the pattern underneath. The end result was an interception that started with strong coverage all the way around.

Despite the fact that Mathieu was going against a lesser opponent, his approach to stopping Harris was sound.

One has to give credit where credit is due, considering that Mathieu is a lot further along than most thought he would be. Yes, it’s only preseason, but these three breakdowns confirm his role with Arizona. When the opposition uses three or more wide receivers, he will be assigned to the slot. When the opposition uses fewer than three wide receivers, he will play free safety.

His role with the Cardinals will be extremely important. Covering the slot is one of the hardest things to do, so he will have an uphill battle on his hands all season long. The good thing is that Mathieu is a sound technician with a high football IQ.

Couple that with his instincts, and you now have a very valuable player who needs to be on the field at all times.

As the season presses on, Mathieu will need to continuously improve as a blitzer and run-stopper and in pass coverage. A rookie’s biggest downfall usually relates to consistency; it’s rare for a first-year player to not have a poorly graded game every now and again.

If Mathieu can manage to grade out positively more often than not, he will be one of the most valuable pieces of Bowles’ defense by the end of the year.

That is exactly the way head coach Bruce Arians and general manager Steve Keim envisioned it.