He's a development guy who blossomed at the tail end of last year when given the opportunity to start due to Seymour's injury.
He's been a situational player with modest success prior to that. From a measurables standpoint, he's built himself up physically to play the 3.
Signing him, means betting on a short track record of success. But the market is barren of guys with his talent. So it's good timing for him. It's a good sign that he's developed into a quality 3 tech pass rusher. Guy knows how to work.
He was tendered a high offer last year, so despite the fact that he wasn't a featured starter, Oakland thought highly of him. From reading Raiders fan thoughts on him, they are genuinely sad to lose him. It's not a shock that Oakland still wants to resign him.