I'd have to look a little deeper before that became a concern for me. For example, even though the Cardinals may have had the lead, was it situations where they built a lead early, but then the offense went completely south and the defense spent the whole second half on the field, and by the time for the winning drive, they were totally spent? Or were there key injuries in some of those games that cost them? There can be a lot of reasons besides 'the defensive coordinator was the problem'.

Besides, he wasn't the DC in Arizona...

Besides besides, I once saw the Packers hire the offensive coordinator on the 32nd (out of 32) ranked offense in the NFL to be their head coach. And that guy got them a Super Bowl title, with an offense that throughout his tenure was routinely top 5 in football. As they say in stocks: past performance is no guarantee of future results...