<P> Under American rules a fumble may be confused with a muff . A muff occurs where a player drops a ball that he does not have possession of, such as while attempting to catch a lateral pass or improperly fielding a kicking play such as a punt (you cannot "fumble" a loose ball). Ball security is the ability of a player to maintain control over the football during play and thus avoid a fumble . </P> <P> If the ball is fumbled the defensive team may recover the ball and even advance it to their opponents' goal . The same is true for the offense, but usually when the offense recovers the ball it simply tries to down it . In American football the offense cannot advance the ball if it recovers its own fumble on fourth down, or in the last two minutes of a half, unless the ball is recovered by the fumbler (there are no such restrictions in Canadian football). However, if the offense fumbles the ball, the defense recovers and then fumbles back to the offense, they would get a first down since possession had formally changed over the course of the play even though the ball had never been blown dead . In American football, there is no separate signal to indicate a fumble recovery . If the offense recovers its own fumble, the official will indicate the recovery by a hand signal showing the next down . If the defense recovers the fumble, the official will indicate with a "first down" signal in the direction the recovering team is driving the ball . Some officials have erroneously used a "first down" signal when the offense recovers its own fumble and the recovery did not result in a first down . </P> <P> This is not the same thing as when a forward pass is attempted and is not caught . In this latter case, it is simply an incomplete pass . However, if the receiver catches the ball, but then drops it after gaining control of the ball, that is considered a fumble . </P> <P> Any number of fumbles can be committed during a play, including fumbles by the team originally on defense . Most famously, Dallas Cowboys defender Leon Lett fumbled during Super Bowl XXVII while celebrating during his own fumble return . </P>

Nfl rules can the ground cause an incomplete pass