Hemingway is a perfect example of why a "size/speed" metric isn't perfect. Yeah, the guy has very good size at 6'1", 230 lbs. and ran a 4.53 at the combine. He also has nice hands and runs good routes. However, you watch him on the field and he's got absolutely zero initial burst. Slow as shit.
It's why he's a great gunner on special teams as he can build up his speed and start moving over a longer field.
Avery and Jenkins are kind of like that too.
McCluster, while he ran a slower 40 time than Hemmingway, has much better initial quickness.
What you really want is a guy that has both. Beckham, Cooks, Watkins, Moncrief have that. (Personally, I think someone is going to get a real gem in Moncrief in this draft. Second round most likely, but I wouldn't be upset if he was the Chiefs first round pick.)