You asked if the guy was on our team - we answered - and now you are going to tell us that it is moot because he is oft injured? You're tough to please.
So I will try harder.
1st - assuming Glenn is injured - you now have Crayton into the lineup. My sig speaks for what I feel about him. Though he isn't the fastest guy ever, I like him running a quick slant for a few yards, especially with his YAC ability. Regarding Key - not quick, but also dangerous on a slant play.
2nd - Quincy, regardless of what you think of his hands, has the speed, which is what you were asking us to identify. He makes drops, but he catches a ball here and there too. I guess we have to take our chances.
3rd - You asked who could get up the seam. That is what Witten excels with - he is a nightmare for LBers, and on 3rd and long, the safeties are already watching 3 WRs.
4th - I have named 4 potential receivers and what they bring - now, since you have refused to accept running a draw or a screen (which works pretty well for some teams, such as GB), Julius is still pretty speedy. Send him in motion to the slot, and I want to see what he can do as a receiver.
Finally, if all of that doesn't satisfy you, I am sorry. But the fact is, regardless of the speediness of a receiver, NO receiver in the NFL can hope to consistently 'break open' on 3rd and 11. It isn't as if any team excels in converting 3rd and long. If we get into such a situation often in the first place, we have problems that supercede an issue of 'not enough speed.'