Pro Days Highlight Key Differences in Top WRs Cooper, Green-Beckham, Parker

A clear-cut top wide receiver has yet to emerge among the 2015 NFL draft class. Whoever is drafted first will be the result of a team's preference.  

Three of the class' top prospects at the position—Alabama's Amari Cooper, Louisville's DeVante Parker and Oklahoma's Dorial Green-Beckham—attempted to stake their claim as the alpha dog on Wednesday during their team's pro days, but all they accomplished was further defining themselves as the type of prospects they truly are. 

At the NFL Scouting Combine in February, West Virginia's Kevin White did his best to separate from the pack. The former JUCO transfer did so with an an impressive 4.35-second 40-yard dash at 6'3" and 215 pounds. 

Size and speed alone aren't enough, though, to completely distance White from the likes of Cooper, Parker and Green-Beckham. 

Cooper, in particular, remains White's primary competition to become the first wide receiver off the board once the draft actually begins. 

Hall of Fame wide receiver and ESPN analyst Cris Carter discussed the differences in Cooper's game compared to White's prior to the start of the pro day. 

"So to think that he's not as fast as Kevin White, I would beg to differ because on the football field, when you put the pads on, he's as fast as anyone playing the position," Carter said on Sports Center, via Al.com's Michael Casagrande. "He can run any route. He has route discipline ... if I was doing a text book of how you run this route, a post corner against a safety, it would be exactly like him."

The Alabama product isn't exactly a slouch in the speed department. The Crimson Tide's all-time leading receiver was only a step or two slower than White with a 4.42-second 40-yard dash at the combine. He stood on the previous number during the pro day and did not run in that particular event. 

What separates Cooper from the rest of the pack, though, is polished route running and his ability to separate from defenders. 

The reigning Biletnikoff Award winner isn't a traditional X-receiver who wins off the line of scrimmage with size and raw athleticism—Detroit's Calvin Johnson or Cincinnati's A.J. Green immediately come to mind instead. 

Cooper is the type of receiver who will excel off the line of scrimmage as a Z-receiver or in the slot. 

Carter continued his explanation of Cooper's skills:  

"

He's dominant in the slot. You can't play bump and run coverage because he's so quick with great acceleration off the ball. He has great football speed. When he's on the football field, he's just as fast as he is in shorts doing the 40 time.

He typically always makes the first player miss. If you see him against SEC competition the last three years, he has destroyed the competition and most of the time, he has been the best player on the field. [Alabama offensive coordinator] Lane Kiffin does a good job of moving him around, so he can retain a lot of information.

"

It's the quickness and fluidity Cooper shows in his routes that will have some NFL team eager to select the nation's receptions leader. 

ESPN.com's Greg Ostendorf provided an example of Cooper's smooth route running: 

The Alabama receiver makes it look easy. He drops his hips and accelerates out of his cuts without losing any momentum. 

Once the workout was completed, the SEC Network's Greg McElroy asked Cooper what makes him the best wide receiver in the draft. 

"I've been doing it for so long," Cooper told McElroy. "I think it's innate. I can do everything a coach asks me to do." 

While Cooper delighted with his route-running ability, two physical specimens were also working out in front of scouts and NFL personnel. 

At 6'3" and nearly 210 pounds, Parker's length and athleticism helped him regularly make acrobatic catches for the Cardinals. 

His size even caught the attention of one scout in attendance at Louisville's pro day, according to Scout.com's Michael McCammon: 

Parker glides along the field due to his angular frame. It never appears as if he's running full speed. Thus, his overall route-running never looks as smooth as Cooper's. 

The Louisville Courier-Journal's Jonathan Linter provided a small glimpse of Parker coming out of his break during the pro day: 

Where Parker truly excels is his ability to adjust on the football. With 33 1/4" arms, Parker's overall catch radius is actually greater than Green-Beckham's. 

The 6'5", 237-pound Oklahoma product, via the University of Missouri, only claims 32 1/2" arms. Teams, however, aren't overlooking his impressive physical prowess. 

Cooper wins with nuance. Parker overcomes with length and unbelievable body control. Green-Beckham, meanwhile, is simply physically overwhelming. 

The receiver, who sat out the entirety of the 2014 campaign due to NCAA transfer rules, impressed with a sub-4.5-second 40-yard dash at the combine. His overall workout turned heads due to his natural size. Green-Beckham even tried to improve upon a few of the marks to varying degrees, as noted by Dynasty Fantasy Football's Fusue Vue: 

Green-Beckham doesn't have to live up to Johnson's standard, though, to be the top wide receiver selected in this year's draft class. Johnson was a once-in-a-lifetime talent. But 6'5" wide receivers with Green-Beckham's natural ability don't come around too often. 

The nation's all-time leader in receiving yardage at the high school level is an automatic deep threat and red-zone target. 

SoonerScoop.com's Eddie Radosevich provided an example of Green-Beckham's ability to track the football during a deep pass at Oklahoma's pro day: 

Physically, there isn't a wide receiver in this year's class as talented as Green-Beckham. The concerns stem from off-field issues that led to his dismissal from the Missouri Tigers football program. 

Teams will need to be completely comfortable with the person as much as the football player for him to warrant a top-10 selection (or even a first-round pick). 

The wide receiver certainly won the public relations battle Wednesday, according to The Oklahoman's Jason Kersey: 

Organizations will exhaustively research Green-Beckham's background. The comfort level they establish will determine exactly where the wide receiver is eventually selected, and there is still an outside chance he could be the top prospect off the board based purely on natural ability. 

Whether it's Cooper, Parker or Green-Beckham, all three wide receivers are intriguing options for any team in need of improving their skill positions. Each of them is in play during the first round. Their pro day experiences only helped build their cases. 

Which of the three comes off the board first is entirely dependent on how each is viewed by the first wide receiver-needy team ready to address the position at the top of the draft. 

Brent Sobleski covers the NFL draft for Bleacher Report. Follow him on Twitter @brentsobleski.