I would say some sort of former playing experience would be necessary given how much they rely on Joe for his "expert" advice. If he's just reporting on practice, games, etc that's fine. However when he's also expected to be an expert on player evaluation, play calling, etc., I don't see how he's qualified in that respect.
That's why when see nfl analyzed on espn, it's by former players (not sideline reporters).
When it comes to X's and O's and player e v a l (which he acts like he's an expert), what are his qualifications?