The difference between guys like Kupp, Adams and Brown and Harry/Burks is quickness. Harry and Burks are big dudes who don't have the short area quickness and aren't fluid with the change of directions.
I disagree that Harry's issues aren't physical. His issue is that he can't create separation because he's not quick imo and his hands are good enough to consistently win contested catches.
I think he's fast straight line if he can build up speed, but it takes him a long time to build up speed because he's not quick. I guess my issues with them is less speed and more quickness/acceleration.
I'm not disagreeing with you on your overall take, as Burks's 3cone and shuttle were worse than Brady's, but here are the 10yd splits (official/electronic) for the players involved:
Kupp 1.62
Burks 1.57
Harry 1.62
Dev Adams 1.64
AJ Brown 1.56
Others PB WRs for reference:
Ja'maar 1.59
justin jefferson 1.57
deebo samuel 1.6
SDiggs 1.53
mike evans 1.6
Burks gets up to speed (acceleration) just fine in a combine setting (although there are a LOT of historically fast 10yd splits this year, so I'm still skeptical on that 1.57). I'll leave it to the experts to evaluate short range "game" speed, as I don't have the knowledge for that.
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Harry's problem is upstairs, I think, after Ian showed that delayed start off the LoS. He needs a change of scenery where he can just see ball and catch ball as opposed to trying to figure out "calculus."
N'Keal : The thing is, Bob, it's not that I'm lazy, it's that I just don't care.
Bob K: Don't... don't care?
N'Keal : It's a problem of motivation, all right? Now if I work my ass off and the Patriots win, I don't see another dime [disclaimer - don't know his incentives in his contract], so where's the motivation? And here's something else, Bob: I have eight different bosses right now.
Bob K: I beg your pardon?
N'Keal : Eight bosses.
Bob K: Eight?
N'Keal : Eight, Bob. So that means that when I make a mistake, I have eight different people coming by to tell me about it. That's my only real motivation is not to be hassled, that and the fear of losing my job. But you know, Bob, that will only make someone work just hard enough not to get fired.