On the whole, college football coaches get along because they understand each other better than anyone else.
But there are a few relationships that were fractured on the recruiting trail or because of past dealings.
In the case of Mack Brown and Bob Stoops, it seems these two have faced off so many times that there was no choice but to have some bad blood develop.
Not all of the great coaching rivalries are bitter or even long-term; some are the byproduct of where they coach.
Here's a look at 15 of the best going today.