Nowell not fast enough? I keep hearing this rubbish and would say that he would give anyone who plays for England a run for their money. Yes, Watson is quicker, but he's the exception, and I would pick him and Nowell for any England squad, not just for their speed, but because they are the best.
He really, really isn't; though setting the bar at "those who play for England" seems a little restrictive - after all, the winger is supposed to be the fastest guy in the team. Against Wales this 6N, chasing a kick forward he was burned by Brown; and then both were burned by Youngs. He'd also [IMO] get burned by Watson, JJ, Care and probably Ford; Alex Goode would give him a good run for his money.
Outside of the England team but sticking with wingers eligible for selection, he's got nothing on Varndell, Wade, May, Rokoduguni, Ashton, Lewington, Short, Woodburn and others. Actually, I struggle to think of a winger [or even FB] in the prem who I wouldn't back to beat Nowell in a foot race over 40m - Banahan and...
I just have this image in my head from the 6N - against Wales IIRC; of Nowell chasing a kick deep; being skinned by Brown, and then both being skinned by Youngs.
Nowell is a fantastic rugby player; he just doesn't have international wing-level pace. Had Exeter played him at 13 or 15 for the last couple of years he'd probably be my first choice for England - or at least presenting a genuine challenge to JJ and Daly.
Having said that, I'm a fan of positions having absolute requirements that simply have to be filled.
A prop has to be good in the scrum
A hooker has to be a reliable thrower
Locks have to be masters of either the lineout or the maul (preferably both)
BSF have to be destructive/workhorse tacklers
OSF have to rule the ruck
SH has to be able to pass the ball and boss the pack
FH has to read and control the game
Centres have to have a balance between distribution, pace and bosh
Wingers have to have top-end pace, ideally alongside acceleration over 3m
FB has to be a rock under the high ball, and a solid last line of defense.
Things beyond that are nice; but however good someone is at the secondary requirements, and absence of the above simply cannot be covered (at the top level).