When you check out the highlights (repasted below), as far as his physique, check out the dude's haunches. To use an analogy, if the average NFL DE compared to mere mortals has a Dodge Charger 426 hemi power plant there, Clowney has a nuclear reactor!
After looking again, in his junior year, his get off was insane. In some cases he was already by the OT before they had even gotten into a stance. He has the suddenness, burst and short area acceleration of a player 100 lbs. lighter, you don't see that every day. Adalius Thomas was one of the better athletes I've seen at the LB position (NE rookie second rounder Jamie Collins is one of the best in the league currently, he played safety (?), OLB, ILB and DE in college, broke the Combine broad jump record set by Calvin Johnson, Brian Urlacher was a college safety at New Mexico and Ahmad Brooks a Virginia LB - they are the only NFL LBs I know if that were good enough athletes to be collegiate kick returners - Brooks and D.J. Williams were among the higest recruited dual threat RB/LBs in the nation... fellow alum John Madden said Williams was the only prep player he ever saw that he thought could have gone directly to the NFL if rules permitted it, I thought Adrian Peterson may also have been able to)... he could play DE, and even do a good job in coverage, I think he lined up at DB at times in exotic formations.
Anyways, Clowney, at his best, reminds me of some of these kind of freakish athletes in his elite movement skills and COD (change of direction) ability for a big man... it isn't an accident that I almost need to invoke LBs to reference and cite athletic comps (though Peppers had cartoonish athleticism, another Panther said they once saw him in practice leap in the air to block a pass, get lowbridged or undercut and flipped in the air, landed on his feet like a cat and still chased down the ball carrier and made the play downfield!). To defeat your offensive counterpart, it helps to have superior talent and athleticism (technique comes into play, as well as things like toughness, physicality, effort, intensity, etc.). In the below Patrick Willis highlight**, Josh Sitton at the 2:30 mark talks about how Willis reminds him of a RB in the way he presses the hole and cuts inside the hole to make a play (never heard it put like this before, but it makes sense if you watch the clip), how he sets up blockers, and you can see an example at the 3:00 mark how he beautifully undercuts the block attempt of the opponent who doesn't even get a hand on him. Not just compared to the OL position opposite him, but if Clowney is a better athlete than some RBs (and even some WR/TEs) he is trying to tackle and bring down, that is a handy attribute to bring to the table.
* 2012
** Patrick Willis NFLs Top 100 Players file...