I think McDonald had his pick of jobs, and chose the Seahawks based on D-Line talent, and John Schneider's philosophy. I think JS is more "start in the trenches" than Pet was, and this will benefit the defense.
With our D-Line talent (Hankins, JReed, Weaver, Byron, etc, etc), I think McDonald will adjust his defense to "stop the run" on early downs, then tear up the QB on 2nd and 3rd downs. Where do I get these 'feelings?' I cram all I see and read in to my brain, let it gestate, then spit it out through my "keyboard konsciensceness." Which means nothing. But it sounds great.
But seriously, I think our defense is going to kick ass right out of the gate.