Nix is playing well, the Irish defense probably needs him to completely dominate the middle as he did often last season if they're to reach a BCS Bowl. He was a force vs. Oklahoma last October.
Junior Defensive End #7 Stephon Tuitt: Part II of Notre Dame's returning All-America tandem up front, Tuitt's expected impact has been lessened by off-season hernia surgery and approximately 20 pounds gained as a result. Tuitt was an explosive, destructive force through the first half of the 2012 season (the hernia occurred during a mid-October game vs. Stanford). Thereafter, he was merely solid, and that's how he started 2013 as well. But Tuitt appeared much quicker last week in a win over Michigan State.
Oklahoma's offensive front gets him in much better shape than he started the season (he was noticeably stiff vs. Temple and Michigan), but for all the hand-wringing about his performance and "bad weight" it's worth noting he was still able to make a game-changing, diving fingertip catch in the end zone vs. Michigan for a score. Not many 6'6" 320-plus pounders could dream of the same.
Sophomore Safety/Nickel #22 Elijah Shumate: A true sophomore, Shumate won a starting safety spot last week over incumbentt Matthias Farley. Both will play in the base, nickel and dime packages (a three-man rotation with Austin Collinsworth), but it's Shumate who's also recently resumed his 2012 role as the team's nickel defender in the slot. To be blunt, Oklahoma's cat-quick receivers will riddle Shumate all afternoon if he's left on an island as he was vs. Michigan State.
The move of Shumate back into the role over freshman cornerback Cole Luke was due partly to Luke's struggles vs. drive routes. I think the defense would be better off with Luke learning on the job, allowing Shumate to do what he does best: hit.
Sophomore Cornerback #6 Keivarae Russell: Thrown to the wolves as a true freshman last season (he never played cornerback in high school), Russell competed vs. the Sooners in last year's meeting, recording nine tackles including one for loss, and doing exactly what was asked of him: make the tackle after allowing the short catch.
That's likely to be part of the plan this week as well, though the staff now trusts Russell more in man coverage, especially in nickel situations. He's been susceptible to the slant route to date, though he recorded three breakups last week vs. Michigan State, one on a third-down slant late in the game to force a punt. More athlete than polished cornerback, Russell has been much better the last two weeks than he was vs. Temple or (especially) Michigan.
Junior OLB/DE/Nickel #11 Ishaq Williams: At some point Saturday, Oklahoma fans will see a 6'5" 255-pound gazelle close on Blake Bell in the pocket as the crowd roars its approval following a third-down stop. But for most of his 35-45 snaps at various positions pending the defensive package, Sooners and Irish followers alike will barely notice #11 exists.
Williams quietly played one of his best games of the season last October in Norman, running with Oklahoma slot receivers down the seam, applying late pressure in the nickel, and playing more snaps than the starter at his boundary linebacker position, Prince Shembo. Both will play extensive minutes Saturday -- but Shembo (a ferocious pass-rusher that struggles in short zone coverage) rarely goes unnoticed. It's time for Williams, a former 5-star recruit -- to make his presence felt more than once a game as well.