He inherited a woeful defense. Very oklahoma esque, in that there was plenty of talent but they rarely executed at a competent level (at least by OSU standards).
To put it into context, in the CCG vs Sparty, Braxton ran for 142 and Hyde added another 118. That should be enough to comfortably put them away (and they almost won if not for bad playcalls to get a 1st down). But instead Sparty did whatever they wanted, and Josiah Price went uncovered the entire night (just to make sure no one confused their efficiency as the byproduct of their NFL talent at other positions).
A week before that against a 5 loss Michigan team, they put up 526 yards of offense, almost 400 on the ground. They barely survived a 2 pt conversion failure to hold off for the victory.
The secondary was surprisingly weak, especially since they had plenty of talent (and would produce a 1st round CB after that year).
The next year they played far more sound football, implemented rugby style tackling, and overall leapt many levels in terms of maximizing talent. Journeymen like Steve Miller and Curtis Grant took big steps forward to becoming solid role players (as starters).
That defense was just as impactful as the OSU offense, which received more of the fanfare.
Many were hoping he'd come back to OSU right now, with the giant loss of Jeff Hafley last week (DB coach -> Boston College HC). There was a schematic concern there though that he wouldn't mesh with Mattison's style, and obviously Texas had him lined up and probably gave him more responsibility.
The irony here is that he helped Urban get outside of his tendencies and run a more balanced attack. After he left, Urban promoted his rock star OL coach to an ill-advised appointment at offensive coordinator and they wasted the most stacked roster in OSU offensive history.
Braxton Miller and Curtis Samuel were the 5th and 6th options, depending on whether they were even on the field.