by Cian Fahey

On Sunday in Arizona, St. Louis Rams running back Todd Gurley stole the headlines. Gurley guided the Rams to an unexpected victory by accumulating 146 yards on 19 carries during his full debut. It was a startling display from the 21-year-old because he had just returned from the torn ACL injury he suffered during his final season at Georgia. Gurley is a special talent who will continue to develop into one of the game's finest players at his position, but he is still at an early stage of that process.

While Gurley was highlighting the advancements medical science has made to get players back on the field quicker than ever, Tyrann Mathieu was showing off the benefits of time. Mathieu tore his ACL towards the end of his rookie season in 2013. The free safety/slot cornerback wouldn't make it back onto the field in time for the start of his second season, making his debut in Week 2 instead. Although Mathieu was back on the field that early, he was never truly himself during his second season. As Mathieu himself will attest to, he was both physically and mentally hampered by his surgically repaired knee.

Mathieu played the 2014 season with a bulky knee brace. The brace obviously helped to secure his health, but it physically weighed Mathieu down and hampered how comfortable he could be in motion. Speaking to AZCentral last year, Cardinals head coach Bruce Arians suggested that a knee brace would have a greater impact on Mathieu than most players: "When you play the position that he plays, any lack of mobility frustrates you, especially him because he is cat quick." Mathieu himself didn't echo or dismiss those sentiments; he was more concerned with being mentally slowed. Speaking to AZCentral after the season, Mathieu said "I've never thought about it as hard as I did last year. I was always thinking about something, rather than just going out there to play."

Through four games this season, it appears that Mathieu is no longer thinking too much. The Cardinals may have lost to the Rams, but that was their only loss of the season so far and Mathieu has been a key cog in their success.

What makes Mathieu such a valuable player is his versatility. Playing safety in the NFL is extremely difficult nowadays because the spread-out offenses that permeate through the league are designed to exploit space. Safeties play in more space than anyone and have to be significant contributors both in coverage and against the run. If you have a narrower skill set, offenses are now better equipped than ever to exploit the aspects of your play that don't measure up to your strengths.

One of the biggest challenges a safety can face is covering a tight end in man coverage. Tight ends these days are some of the most athletic players in the league. They are specifically being drafted for their size and athleticism to take advantage of one-on-one matchups in space. In the above play from Sunday, Mathieu is lined up as a boundary cornerback against Jared Cook. Cook isn't one of the best tight ends in the NFL, but he is a very impressive athlete. Significantly, he is also 6-foot-5, compared to Mathieu's height of 5-foot-9.

Cook gets the better of Mathieu releasing from the line of scrimmage. Mathieu's feet are heavier than is typical, giving Cook an opportunity to accelerate past his outside shoulder. Because of this, Mathieu is incapable of getting on top of Cook's route to then turn around and locate the football. With his height, this is the worst spot for Mathieu to be in against Cook. Cook has positioning on the ball and Mathieu is in prime position to be called for defensive pass interference.

How Mathieu recovers to this scenario is very impressive.

In this situation, most defenders panic and play the body of the receiver. They press tighter into the offensive player's body to prevent them from playing the ball. This can be effective, but it's also an easy pass interference call for the officials. Mathieu doesn't panic in this spot. Instead, he keeps his distance from the tight end and watches how he uses his hands. Mathieu is able to perfectly time his actions so that he sweeps through the arms of the tight end as the ball arrives, preventing the tight end from getting the touchdown.

Mathieu not only had to show off outstanding timing, awareness and discipline to disrupt Cook at the catch point, he also needed the strength to impact the tight end as much as he did. Mathieu may not be a tall player, but he is well-built and showcases power in different ways.

One of the ways he showcases his power and precision is by going after the football. Mathieu may not have many forced fumbles to his name at this point in his career, but he consistently tests opponents' ball security both at the catch point and in tackles. Against Gurley, Mathieu was able to force the rookie's first career fumble. Mathieu made a great play on the ball, locating it and striking through it at speed to knock it free.

Even though the Cardinals as a whole struggled to contain Gurley during the second half of their matchup with his Rams, Mathieu was a consistently impressive run defender.

The safety understands space and how to work away from blockers while also having the power to impact receivers and tight ends in tighter situations. His intensity and quickness in tight areas makes up for any potential problems that could occur because of his size. It's this combination of traits that allows him to play as a slot cornerback and strong safety as well as a free safety. Although those types of plays are hugely valuable, Mathieu's most impressive play against the Rams came when he showed off his athleticism in pursuit.

In the above image, Mathieu is highlighted playing off coverage in the slot to the left. The Rams are going to run to the right side of the defense, away from Mathieu.

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Even though Gurley gains 52 yards on this play, Mathieu doesn't deserve any blame for that. Mathieu was the reason the play didn't gain 68 and a touchdown. He not only worked across the field very quickly, but he actually chased Gurley down after the running back had pulled slightly ahead of him at his own 37-yard line. With a few more months of training, Gurley likely finishes this run, but even considering the running back's limited conditioning, this is still an incredible recovery from Mathieu.

Gurley is a world-class sprinter. He ran 100 meters in 10.7 seconds back in 2011, when he would have been a less physically developed teenager. Questioning if that speed remains after his ACL tear would be fair, but he showed off that caliber of speed on a number of occasions in this game, including on this run. Only a few players in the league could have caught him from behind after working across from the other side of the field as Mathieu did here.

Mathieu's controlled athleticism is key for his success. It's what allows him to be so comfortable in different types of man coverage.

Previously we saw him line up in press and prevent Jared Cook from scoring a touchdown despite being beaten early in his route. On this play, Mathieu's work through the break of the route is crucial. The safety initially lines up across from Anquan Boldin but switches onto Vernon Davis at the snap. Davis is running a deep corner route. Mathieu is initially outside of Davis when the tight end enters his break. He has to plant his foot and swing his hips open like a gate to shift his weight. Shifting his weight allows him to reverse his momentum and undercut Davis' route.

When Colin Kaepernick's pass is underthrown, Mathieu is in position to make a comfortable interception. This kind of precise footwork and quickness is rare, and it's the kind of movement that Mathieu struggled to make when playing with a brace last season.

Mathieu can excel in off-man coverage but is also a very impressive when tasked with playing in underneath zones. On this play against the New Orleans Saints, he shows off perfect technique to stay on top of the tight end's route through his zone and has the awareness to stick with him further downfield as the play is extended. Mathieu is always in position to see the ball coming while giving himself the leverage to attack it ahead of the tight end if it is thrown his way. Mathieu's versatility to play both man and zone coverage so effectively affords the Cardinals coaching staff more flexibility with their play calling. That lends to the unpredictability of the unit as a whole.

His athleticism and discipline also allow him to blitz from different spots of the field or line up as a single high safety. This furthers his contribution to the unpredictability of the Cardinals' whole defense.

In the above play from the Week 2 matchup with the Chicago Bears, Mathieu initially lines up as the deep safety. He is aware that there is a lot of time left on the play clock, so Mathieu advances towards the line of scrimmage. He puts himself in a position to threaten as a blitzer, leading Jay Cutler to adjust his protection and point out Mathieu as the Mike. Having disrupted the protection schemes of the offense, Mathieu begins dropping back into his deep position just before the ball is snapped. He is deep enough to still be effective as the team's deepest defender by the time Cutler has the ball.

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Mathieu is a key player for one of the best teams in the NFL. He has a backstory that is notable, but not one that should define him. Mathieu himself recently spoke to the Dan Le Batard show about wanting to move away from the nickname that outlined his persona during his time at LSU.

The quickest way the young defensive back can make people forget about his past is by making his present more interesting. If he continues to play like this, his present is going to be more interesting because he will be one of the best defensive players in the NFL. Mathieu still has a ways to go in terms of proving his longevity, but he is the closest thing the NFL has to what Troy Polamalu was during his prime.

He is a disruptive, explosive player who can line up anywhere on the field to be effective against any type of play call. Mathieu is the rare player who intimidates offenses by simply being on the field.