I think it's important to realize that most of the press who sets preseason expectations are idiots, and if we are really going to determine who had the best coaching performance throughout Big 12 play, we should disregard that completely.
The candidates
Bill Self
Coach Self brought KU into conference play with a disappointing loss to MSU as the only real blemish on the resume, but it was clear to anybody watching the Hawks play that they had some serious holes. It took a miracle last second 3 to send a game into overtime at home against "Mayor of Ames, Town Fool of Everywhere Else" Hoyberg. Then, the Hawks lost 3 straight games to OSU, TCU, and OU. It looked like they were headed for a similar downward spiral to the one Texas suffered after losing at KSU when they were ranked #1 a few years ago. Most coaches would have lost that team and would be staring at a 9 seed and likely first round exit right now. Getting KU where they are, despite getting much more help at the top of the rankings than a team would get in a typical college basketball season, is pretty remarkable.
oscar Weber
Coach Weber was a very polarizing figure coming into the 2012-13 season for the Kansas State Wildcats. Until he pulled out a convincing victory against Florida at the Sprint Center, it looked like Weber was not going to win a single quality OOC game, and lose every game against a quality opponent in blowout fashion. Despite that victory, even the most optimistic wildcat _fans were very skeptical that Weber would be able to outdo Frank in what was clearly a very down year for the Big 12. Weber has gone on to win the games he should be winning, only losing games to teams that are either better than his team or games in difficult environments like Hilton Coliseum. Weber doesn't really have a big win in conference play, though, with the game in Stillwater being his final chance to get one. Weber has done a fantastic job getting his team to buy into his system in just his first year as head coach, and has set himself up nicely for COTY contention.
It's a close race, but I would give it to Self by a hair at this point. Obviously the results of the games on Saturday could change that.