I think Riley may have hired the wrong guy in addition to the systemic issues he creates for his defense. The high reps vs HUNH creates a lot of bad habits. The lack of contact in practice tends to manifest as poor tacking and less physicality. The quick strike offense doesn't control the ball or give the defense a rest and that's true with Riley to an even greater extent than it is for Leach's short passing game.
On top of that, the more I look at Grinch, the more I think Riley hired the wrong guy. Even in his one good season at WSU, his unit was gashed by most of the good running teams they faced and especially by those with a true dual threat QB (they were blown out by Arizona and Michigan State). There were 3 reasons Grinch looked good that year, relatively speaking:
1. The Pac-12 was well into their current decline by then.
2. His defense stuffed some real bottom dwellers, especially FCS Montana State and MWC cellar dweller Nevada from their SEC worthy non-conf schedule. Impressive statistically but not so much if you look at what actually happened.
3. Hercules Mata'afa was able to create an interior pass rush and his quickness was often able to disrupt the blocking and compensate for a scheme whose shifts often left a front that was not gap sound. Teams that could run the ball feasted on the lack of gap integrity. Against Zona, Cal, Washington and MSU Grinch's defense looked a lot like Manny _iaz had moved to Pullman.