For some reason, SB losers very often collapse, especially when its not a young up-and-coming team. The Patriots were due for a significant setback even before Brady went down.
You hit it right on the money there FYO. Since the 2000 season, the Super Bowl loser has failed to make the playoffs the following season. The only exception is Seattle in 2006 after losing the 2005 Super Bowl. And they went 8-8 that season and only made it because they won their division (with an 8-8 record??). Any other division in football and they're out of the playoffs that year.
Let's see if New England keeps up that trend.