During the third quarter of the Chargers/Steelers AFC divisional playoff game today, the Steelers picked up a loose ball and took it into the endzone for an apparent touchdown. Raise your hand if you knew it was coming back, despite the lack of a penalty.
Mine is raised. The rule is uniform across all levels of football.
On the play, Eric Weddle was engaged in a block on a punt to the Chargers. The punt ended up being a bit short of Chargers' returner, Darren Sproles. The football ended up hitting Weddle on the head. The Steelers then scooped up the ball, and ran it home.
What happened is defined as a muff. When a player touches the ball -- but does not gain possession -- he is said to have muffed the football. By rule, a muff can be recovered by the opposing team, but not advanced. This could happen in many different ways. Say the returner just drops the ball. That's a muff, and cannot be advanced. The entire key to the equation is possession. If the returner catches the ball and take two steps with it before fumbling, the return team can most certainly advance the football.
This situation could happen on a kickoff as well. If the ball hits off a member of the receiving team, the kicking team cannot advance the recovered football. If the receiving team gains possession, and then fumbles, it's perfectly legal to advance it.
Just remember the question, on punts and kickoffs: Did he possess the ball?