Was reminded of this by an ESPN Football Outsiders story in a similar vein...
So, the 1994 NFL season. It's week 5. The Eagles are 2-1. The 49ers are 3-1, and they're the Super Bowl favorites. The Eagles go to San Francisco. They play a team that's beaten up on the offensive line, and absolutely embarass the 49ers, 40-8. The Eagles were taking advantage of that offensive line to the point that Seifert pulled Steve Young from the game in the 3rd quarter because he was afraid the Eagles d-line would kill him.
What happened from that point out? I'm sure you remember the 7 losses to finish that season. And I'm sure you remember the 49ers going on to pulverize the Chargers to win the Super Bowl that year.
Another Eagles related example? Look to 2004, and the Patriots team that beat us in the Super Bowl. Week 15, they lost to the Dolphins. The 2-11 Dolphins. And blew an 11 point 4th quarter lead in the process.
If you look at nearly every winning Super Bowl team's schedule, you're going to see a loss that makes you scratch your head and say "how in the hell did they lose that one?". Not saying this team's going to the Super Bowl. But you can't panic about a loss like this. Good teams can overcome it.