I'll start with the measurables:
Cooper Kupp:
10 yard split - 1.57s
Short Shuttle - 4.08s
Three Cone Drill - 6.75s
40 time - 4.62s
Nelson Spruce:
10 yard split - 1.63s
Short Shuttle - 4.20s
Three Cone Drill - 7.09s
40 time - 4.69s
Basically, Kupp's top-end speed isn't great, but he has great acceleration, quickness, and change of direction ability. On the other hand, Spruce's top-end speed is also lacking, but his acceleration, quickness, and change of direction ability range from average to bad.
That all shows up on his game tape. Spruce lacks physical talent. He creates separation through savvy and physicality. It works for him. He will finish in traffic. He makes tough catches. But he tends to body the ball more and doesn't attack it that well in the air. Spruce plays every down like it could be his last. That's something to be commended. Spruce is a slot WR who will have to win working the middle. He won't separate outside and won't win in the air well enough for teams to accept that.
Kupp is a different type of player. He lacks top-end speed, but as I stated, he has acceleration, quickness, and change of direction ability. He has the athleticism to separate consistently. He combines that athleticism with skill and savvy that is simply beyond what Spruce offers. In addition to that, he attacks the ball better than Spruce does, catches the ball in traffic better than Spruce does, and he runs after the catch better than Spruce does. Spruce is essentially Kupp if you strip away the things that make him special.
Kupp is only the third guy I can say this about, the others being Suh and our own Aaron Donald: The more I watch video of Kupp, the BETTER the looks.
Normally, I watch video to break down a player into components and see what I think will translate to the pro level and where he as a rookie will have to improve just to make it in this league. We are certainly familiar with 1st and 2nd round players not working out, so this applies to everyone, drafted and undrafted. Not so with Kupp. The more video I watch, the more boxes he checks.
Can he run all the routes? Check.
Can he separate press and soft coverage? Check.
Can he run after the catch? Check.
Can he make the kind of catch on each play that will make it hardest for the defender to make a play? Check.
Can he take the top off of a defense? Check.
Kupp is one of the FEW WRs I watched that I'm really surprised New England didn't go after because he would be PERFECT in a Erhardt Perkins offense because he has that mentality.
Why teams underrated him the way they did, I dunno (well, I got an inkling, but I don't wanna start anything...) Honestly, I'm kinda glad in a backwards kinda way because I think we got the BEST WR in this draft after rewatching video (on my life, I'd take Kupp over Mike Williams from Clemson every day of the week and THREE times on Sunday...)
Honestly, the ONLY thing he's not likely to be or do is a Calvin Johnson type who will win tons of jump balls.
Beyond that, I think Kupp is gonna be a freakin' STAR.