Starting lb's made some plays, but you can clearly see they lack the athleticism of those backing them up. I think you'll be seeing the 2's more as the season progresses.
That's pretty much my only legitimate concern about this defense was the two LB's in Tanking and Davis. Both are solid LB'ers, but they cannot go east and west very well, which was evident on those speed options Central Arky was running. They had success nailing the spots near the tackles and out to the sidelines, because the LB's were getting sealed off.
Granted, not many Big 12 teams do run speed options, but I can see them doing some variations of this type of plays against K-State, assuming Tanking and Davis continues to be the starters.
And Sullivan should be getting more playing time with the ones (over Tanking or Davis), because he was flying like a scud missile.