The easy answer would be "Cowboys" if they had not been overrated to begin with. They were consensus NFC favorites - why, again?
On the other hand, even after Peyton Manning's knee surgeries, the Colts entered the season looking much as they always look. Their play, their philosophy, the way they approach and perform each regular season has barely changed in the Tony Dungy era.
Now, they're completely unpredictable. They're 3-3, for one thing, whereas they're often still unbeaten by now. They're either losing to or barely escaping teams they have no business even being threatened by. They're playing catch-up in their own division. They seemed cured after throttling the Ravens, then it was all reversed a week later in Green Bay by that pounding by the Packers.
Maybe Manning is hurt worse than he'll acknowledge. Maybe Dungy has hit a wall (he did consider retiring in the offseason). Whatever the case, the team defined by calm and consistency has shown neither. The Cowboys look and act just as you figured they would. These Colts, though, are unrecognizable.