[JeffAtlanta]

No catch because the player has to maintain control of the ball through contact with the ground.

That is the end result, but the lack of a football move before losing control of the ball is the reason it is an incompletion.

The logic is that if a reciever catches a ball cleanly and it driven to the ground by a defender, then the play should be over the instant the reciever's back touches the ground.

The additional requirement of "football move" is what makes the above scenario an incomplete pass.

[steveegg]

Like I said in my initial answer, that particular situation had been re-addressed a couple years ago, prior to the new-for-2005 "football move" rule (for some reason, the 2003 season sticks in my mind). The moment the back (or knee/side/chest/head) hits the ground following contact with a defender, the ball-carrier is down by contact. Because the NFL wanted to take the discretion of whether the defender or the ground caused the ball to pop out away from the refs, they amended the rulebook to make it clear that possession must be maintained through the contact process with the ground.

There is a reason why I made that distinction between the back/knee and 2 feet in that specific case of contact by the defender; 2 feet would mean that the receiver could still attempt to advance, while the knee/back would mean that he could not advance (or are you saying that if the receiver maintains possession after hitting the ground, he can advance the ball unless he's re-touched while on the ground?).

Let's apply that to a slight-hypothetical from yesterday's game. Had Fletcher touched Polamalu as he flashed by and caught the ball, the play would have been over before Polamalu attempted to get up. That process of attempting to get up, while not a "football move" in the eyes of that ref, is a distinctly-different process than that of contacting the ground.