He took Al Golden washouts, brought in recruiting juice and coaching intensity to get the Canes back into a Top 3 position within 3 years. It was too bad MR and JR weren't able to match that improvement on Offense or else the Canes wound have been among the ship contenders the past couple years.
If Saban was needing a DC- he would have probably snatched Diaz in a heart beat.
Miami made the right decision to grab him-- home town boy with big time family connections in the Miami area. It means Manny is from THE CRIB and would fight hard to bring Miami back. Diaz was more likely to be that compared to all the other options last December.
The only mistake i've seen Diaz make is to step away from day-to-day management of the Defense. His hand-off to Baker was a mistake. But he just figured that out and likely Baker is gone when season's over. I guarantee you Diaz will find a good DC.
Handing off the defense isn't a mistake. Leaders delegate. The problem is Baker sucks (so far) and Diaz chose him.