by Cian Fahey

It's only natural that rookies are the primary focus for those of us who spend time watching preseason NFL games.

We're getting our first glimpse of college prospects playing at the NFL level. Even though the schemes are typically simpler and the pace of the game and quality of the opposition don't replicate what is waiting in the regular season, these games are a step above what these prospects experienced in college. Even those facing third- or fourth-stringers are still facing better opponents than they regularly would have in college.

Rookies aren't the only players who must be watched closely at this time of the year.

Free agent additions, backups stepping into starting roles, players coming off injuries and developing youngsters are all clouded in uncertainty for different reasons at this time of the year. One of the most interesting players in any of these categories is Minnesota Vikings wide receiver Cordarrelle Patterson.

Patterson was selected with the 29th overall pick of the 2013 draft after the Vikings traded up to get him.

He compiled just 45 receptions for 469 yards and four touchdowns. Those numbers tied him for the seventh most receptions of any rookie, behind one running back and one tight end; the 12th most receiving yards of any rookie, behind three tight ends; and the seventh most receiving touchdowns. Drops hurt Patterson's production, but the primary reason for his limited impact was his usage.

It was widely understood that Patterson would take time to develop into an all-around NFL receiver when he entered the NFL draft. According to his profile on NFL.com, Patterson didn't play football during his first year in college. In his second year, he played at a junior college before moving on to Tennessee. With just one season of top-level college football under his belt, he entered the NFL draft and became a first-round pick.

Patterson's physical talent made him a first round pick, but his lack of experience as a true receiver limited how he could be used. He barely saw the field during the first half of the regular season, before being used in limited ways during the second half.

This chart recounts each of Patterson's receptions as a rookie and the routes he ran before catching the ball.

As we can see, most of Patterson's receptions came on screen plays. This is largely a reflection of his lack of experience running routes against quality competition, but it also highlights his greatest strength. Despite standing at 6-foot-2 with a very athletic frame and exceptional physical traits, Patterson's greatest strength is his vision with the ball in his hands.

Much like Percy Harvin, the player he indirectly replaced in Minnesota once the veteran was traded to the Seattle Seahawks, Patterson blurs the line between receiver and running back. He can line up in the backfield and he did so to good effect in 2013, but his biggest play came on a screen pass.

Against the Baltimore Ravens late in the fourth quarter of Week 14, the Vikings face a third-and-10 on their own 21-yard line. Patterson initially lines up in the slot to the left, but motions behind the line of scrimmage to the slot on the other side of the field. Lining Patterson up closer to the line of scrimmage allows the Vikings to run a screen play for him, one on which they regularly relied last year.

Importantly, Patterson moves to the side of the field where the Vikings had their running back. That allows the running back to act as a blocker, while his proximity to the line of scrimmage allows the screen to be based on the blocking of offensive linemen rather than wide receivers. At the snap, Patterson moves forward slightly before reversing back to face his quarterback. Meanwhile, his four blockers are getting into position.

When Patterson turns around, he has space in which to work. Initially it appears that he is making a bad decision by immediately running towards the sideline, but he keeps his eyes up and isn't aggressively angling towards the sideline. He is just making sure he runs towards the outside shoulder of his initial blocker. Once Patterson gets behind that blocker, he stretches his arm towards him to push him down the field.

After pushing his blocker, Patterson quickly shuffles his feet and slides inside to run towards the seam. He stays level with the sideline and has a clean running lane because his initial movement towards the outside shoulder of his blocker moves any potential tacklers to the outside of their blockers. At this stage of the play, he needs to use his athleticism to outrun the inside defenders who are trying to recover position.

Patterson makes one obtuse but perfectly timed and effective cut to slide past James Ihedigbo at the first-down marker. From there, he makes another cut that neutralizes the last man to create an easy saunter into the end zone for a 79-yard touchdown.

What Patterson does when he has the ball in his hands is what makes him special. He can be a very effective player in the NFL even if his skill set never evolves past what it was last season. These kinds of plays and some very impressive ball skills make him a dangerous weapon for the offense.

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Not only does Patterson have the size, fluidity, and body control to make tough receptions against tight coverage, he also has the ball skills to locate the football early on so he can beat defensive backs to it. In a way, Patterson has the ideal body build for a wide receiver because he is tall enough to work above defensive backs, but his size also doesn't hinder his flexibility and comfort changing direction.

It should also help him as he is asked to run more routes over the coming years.

Patterson will need to prove his ability to shake press coverage at the line, be consistent with his speed, maintain his balance through his cuts, and understand how to react when the defense tries to squeeze space away from him with more aggressive coverage. He can only prove this over a prolonged period, so to this point we really don't know if he will develop into an all-around receiver or not.

The signs are good though.

For his touchdown against the Detroit Lions in Week 17, Patterson runs a perfect fade route. It's important to note that Patterson is lined up outside the numbers to start this play. Because of that, he needs to be wary of space down the sideline. While he is lined up against a defender who is in position to press him, the defender doesn't initiate contact at the snap. This allows Patterson to step towards him at the beginning of his route.

By doing this, Patterson keeps the defender in front of him and maintains the room between them both and the sideline. Once Patterson runs past his outside shoulder, the defender has no chance to turn his head and locate the ball.

The above GIF freezes for a moment when Patterson gets to the end zone. At that point, we can see Patterson's right leg is extended inside and he is pushing backwards towards the pylon. This creates a pocket of space between himself and the defender trying to cover him. The only way the defender could have defended this pass was if he knocked the ball away at the catch point. Patterson makes that impossible with this subtle movement at the end of his route.

This was a nice route and one to be enthused about, but it was still just one route and not an exceptionally difficult one because he wasn't contacted at the snap.

In Week 2 of this year's preseason, Patterson showed off his ability to work the sideline against one of the better cornerbacks in the NFL, Patrick Peterson. Patterson is lined up to the top of the screen. Again, Patterson isn't contacted at the snap, but Peterson is in close proximity and looking to mirror his footwork at the release. Patterson shows off his very quick feet and deceptive body control with a hard plant inside that causes Peterson to stumble.

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His release gave him a clean running lane down the sideline with space into which his quarterback could throw, but Matt Cassel missed the throw.

Although he had a relatively quiet rookie season, Patterson's outlook moving forward should still be considered very optimistic. Despite his eventful time in college, he is still just 23 years of age and will be until the end of this season. He has already made a number of impressive plays in the preseason this year.

Against the Kansas City Chiefs in Week 3, Patterson had one huge reception for a touchdown on a seam route. That kind of big play is always exciting, but it's something we knew he could comfortably do. It was a reception later in the game on a third-and-5 that highlighted Patterson's development.

Patterson is lined up to the bottom of the screen and is going to run a relatively simple slant route. The cornerback covering him is Sean Smith, a very athletic defensive back. Despite his athleticism, Smith is still concerned with Patterson's ability to beat him down the sideline for a big play. Therefore, when Patterson plants his outside foot quickly after the snap, Smith drifts outside. This gives Patterson the chance to turn infield unopposed before making the reception for a first down.

The degree of difficulty here isn't what is important to note. The ease at which Patterson executed the play is. If Patterson can consistently make this kind of play to complement his big-play threat down the field, it will become very difficult to stop him from being one of the most productive players in the NFL.