Wasn't Wirfs the LT? If so, thats definitely a tough spot to fill as it is one of the more important lineman positions and the team will be breaking in a new QB. I think the D takes a step back, but that doesn't mean they will be bad. A step back from last year can still be a damn good defense seeing how they were stout as heck last year.
Wirfs will be tough to replace because of Iowa's OL depth. Epenesa will be tough to replace if it means that Dowling kid we passed on is taking his place