Where Peyton Manning could slide

Peyton Manning has been impossibly good, but will his luck run out? Dustin Bradford/Getty Images

We at ESPN go out of our way to explain what is happening in sports and why. We hire analysts who have been deeply involved in the sport and have either a feel or an analytical mind for the way games go. With video and diagrams, they can show, for instance, what it is that Peyton Manning sees in floating a pass perfectly over a defender's arms.

But even our experts sometimes say, "I just don't know how he does that."

On occasion, the athletes themselves admit, "I don't know how I did that. I think I got a little lucky." Luck is the remnant of what we can't explain. Fortune may favor the prepared, but no clever pundit has said how to ensure that Lady Luck is always on our side. And when she leaves, those who previously benefited from her attention tend to regress toward their true skill level.

In the 2013 season, we've seen several statistical marks that make us think the smashing success of a player or team is about to slow down.

Here, I've chosen a player, a unit and a team that could all slide a little bit. And we have to start at the mile-high marker of Manning.