Johnny Manziel is such a beast he has a career record of what 20-6 with notable wins against Bama and Duke, and biggest bowl win being the Cotton Bowl. Johnny is one player on a football team, the majority of big 12 teams would have carved that swiss cheese of a defense numerous times the 2 years Johnny was there and would have had better equiped defenses to contain Johnny and that offense as well.
Exactly who in the Big 12 would have done that?
Baylor?

Talkin about the MAJORITY of Big 12 schools would have carved up the D and limited Manziel when in the Cotton Bowl you mentioned, Oklahoma had a chance to do just that and got demolished beyond belief.