Pure Deep Speed / Vertical Threat WR's

[ChiFan24]

I haven't gotten heavily into scouting yet, so I'm deferring to some of you here. The Bears' most underrated need, something I hope they address in the first couple rounds, is a deep threat at receiver. Not a good receiver, necessarily. Just a guy that can sprint down the field on a 9 route and make the defense pay for not giving safety help. Pure speed. Like a pre-crippled Johnny Knox.

This is kind of hard to determine without 40 times available, but going down the list, I'm kind of blanking. Tavon Austin seems to be the fastest, but I don't really think "deep threat" so much as get him the ball in space. Terrance Williams and Robert Woods are a couple guys I saw do it in college, but I'm not sure they fit my "pure speed" criteria in the NFL in that they seem to be 4.45-4.5 type guys. Anyone have any ideas?