When choosing a team 'most likely to not return to the playoffs' one needs to look not only at the team that just made the playoffs, but also what team(s) would likely replace them.
The author does this with his first three candidates (Bengals, Panthers, Cowboys) but neglects to do the same with Denver. While I agree that the Broncos are likely to descend in performance in 2015, my question is what team in that division will surpass them?
San Diego added guard Orlando Franklin to improve their offensive line, and essentially replaced Marcus Gilchrist with Jimmy Wilson in their secondary. Kansas City replaced Dwayne Bowe with Jeremy Maclin, and added guard Ben Grubbs; assuming Eric Berry won't be back from his lymphona, adding Tyvon Branch is a downgrade. Both teams re-signed some starters, so they didn't regress - but I don't know if their upgrades at guard are enough to win the division. The difference is closer than it was, but I don't know if it's enough to assume that Denver will miss the playoffs.