This weekend gave us a taste of just how fragile great NFL teams are.

It started on Saturday, when Seattle knocked off New Orleans. The Saints, of course, won the Super Bowl last year, and were able to keep their cast together for another run in 2010. But the injury bug bit. Losing their top two running backs, Chris Ivory and Pierre Thomas, was a blow. But the Saints of 2010 just didn’t match the 2009 version. The ’09 Champs were plus-11 in the all-important turnover ratio department. This season the same team was -6. Drilling deeper, last year’s Saints took the ball away 39 times, this year, essentially the same group with the same coordinator had 25 takeaways.

The Saturday defense for New Orleans was atrocious. They were on a mission in ’09…and are fortunate…like the ’99 Rams…to have won their Super Bowl.

The same can be said of Indianapolis and their Super Bowl win in ’06. All of a sudden, Peyton Manning has played 13 years in the NFL and turns 35 in March. Realistically, how much more can be expected of Manning? Unless the Colts upgrade his supporting cast, another Super Bowl doesn’t seem to be in the offing.

In more contemporary examples, the Chiefs went 10-6 this year with three-time Super Bowl Champ Charlie Weis as offensive coordinator. Now, he’s off to the University of Florida. There’s certainly no guarantee that the Chiefs will be able to repeat their excellence of 2010 after getting drilled by the Baltimore Ravens.

Along those lines, it looks like Philadelphia will have defections. Michael Vick and Kevin Kolb are both potential free agents, and they’ll have a hard time picking which one to keep. This is 12 years at the helm for Andy Reid in Philadelphia, with nine playoff appearances and no championships.

This is a fragile league, as the Rams learned after 2001, and the Titans learned more harshly…never getting the ring. For Falcons and Bears, especially…and even the Steelers and Patriots, you never know when the success is going to end, and you better take advantage of the chances you have. As Jerry Glanville says, NFL means Not for Long.