Pros: Strikes with great quickness off the snap, even out of a three- or four-point stance - Kerrigan gets up and starts moving forward in a big hurry. Uses his low stance as leverage to explode up and forward. Can "dip-and-rip" very well; he gets low around the edge and uses his hands to separate from tackles as he's turning to establish a pass rush arc, and closes in with a fast re-direct. Fast in doing so to the degree that tackles who don't have a quick kick-step are going to be in big trouble against him. Changes offensive gameplans in that a blocking back is often required to take him out as he gets around the tackle.
Not a great splitter of double-teams, but can ride more than one player outside against the run. As fast as he plays, Kerrigan has a very good eye for misdirection - doesn't get fooled a lot on traps and counters. Blasts off the blocker well when crashing in at an angle. Really good leverage concept for his height (6-foot-4, 255 pounds); he'll get under pads easily and win some strength battles.
Cons: As quick as he is, I wonder if Kerrigan's pass-rush style will work right away in the NFL, especially as a lower weight. He has a decent bull-rush and impressive upper-body strength, but his game is built very much on edge speed, and a lot of tackles at the NFL level will be able to work that out. With a new transition to edge rusher/linebacker obviously in the cards (the weight loss sort of gives it away), he'll need to learn a lot about coverage unless his new defensive coordinator just wants him moving forward all the time. Loses his footing on stunts and loops at times because he's going at Tasmanian Devil speed.
What does he bring?: In the right system - either paired with an elite defensive tackle who can split the blocking load or as a pure "endbacker" in a five-man or hybrid front - Kerrigan has the potential to dominate. He's proven that he has the determination to succeed, and I expect him to excel with his pure speed, first-step burst, and ability to turn the corner.