<!–start image–><!– end image–>Pick the cliché. It’s a rollercoaster, a whirlwind, an up-and-down ride. However trite way you describe the battle for the starting quarterback at USC this spring, you’re probably going to being accurate. The volatile battled continue Thursday with Mitch Mustain back in the normal rotation Go inside for more from practice, including a rep-by-rep breakdown of the quarterback