Georgia Tech Fan
Well how many teams lose a two-deep's worth of players in one offseason. And that's before injury. But to answer your question just off the top of my head Florida went from 11-2 to 4-8 just a couple years ago. And that's a power program.
EDIT: Just remembered that UCF has gone from 9 wins last year to 0 so far this year as well.
I was thinking TCU a few years ago