Matt Cassel released. Vikings? Bears?

On the occasion of Matt Cassel's release by the Kansas City Chiefs, we should review the NFC North's pair of backup quarterback openings. Cassel figures in at least one, if not both, of those situations.

First off, the Detroit Lions (Shaun Hill) and Green Bay Packers (Graham Harrell) wouldn't seem like candidates to be in on the free-agent market at this position. But the Minnesota Vikings have acknowledged they plan to bring in a veteran to compete with Joe Webb to back up Christian Ponder, and the Chicago Bears don't have their 2012 backup (Jason Campbell) under contract either.

Cassel, Campbell and Ryan Fitzpatrick are the top three free agents available. The Arizona Cardinals' Kevin Kolb could soon join them, and as we've discussed, the Vikings and general manager Rick Spielman have a long history with Tyler Thigpen -- dating back to the 2007 draft.

It wouldn't be surprising to see the Vikings make a quick move toward Cassel, who has been a backup for four years and a starter for five in his career. Thigpen could be their backup (backup) plan. If the market continues to dwindle, the Bears might consider Cassel or, more likely, be able to bring Campbell back at a lower price than he might have been seeking.

Now that the first wave of free agency is largely over, these are the kinds of stories we'll be following.