They'd find a spot for him. Nash is the second leading scorer in the conference (17.1) and is a 6'7" versatile/athletic swing forward that creates a lot of mismatches. If you don't think a player like that would start on this OU team, your glasses are an extra shade of crimson.
As I see it, it would force OU to either (1) go smaller with Nash at the 4 (similar to Cam last season) or (2) Nash at the 3 and either Woodard or Cousins coming off the bench. Again, it's not necessarily who Nash would start "over" but rather how his presence would change the makeup of the team.