I can't precisely define irony off the top of my head, but I think this qualifies:

Iowa State will introduce Paul Rhoads as its next football head coach on Saturday evening.
[...]
Rhoads was the defensive coordinator at Auburn in 2008 but found himself out of work with the resignation of Tommy Tuberville.

Rhoades, of course, takes the helm exactly a week after another ex-Auburn defensive coordinator, Gene Chizik, burned the Cyclones by bolting back to the Plains after consecutive losing seasons. If at first you don't succeed ...

Rhoades doesn't quite have Chizik's record as a defensive coordinator, but he has put together two very good seasons at Pittsburgh (5th nationally in total defense in 2007, highlighted by the brilliant finale over West Virginia) and Auburn (15th in scoring D this year) opposite horrid offenses. And, maybe more importantly here, he's an Iowa native with Iowa State ties, as a secondary coach in the very lean years from 1995-99. Rhoads has a great reputation -- the ever-tough Brian Cook wanted him as Michigan's new defensive boss -- but if there's one knock against him, it's that he hasn't been around winners: He was part of some decent teams at Pittsburgh, including the 2004 Big East co-champion/BCS team, but he hasn't coached in another bowl game since.

Of course, Gene Chizik coached on teams that combined to go 26-0 the two years before he came to Ames, and look how that turned out.