Originally Posted by duff18
It is my understanding that the d-lineman has to enter the neutral zone and force the O-lineman to move in order for it to be offsides. Technically a d-lineman can do jumping jacks and cartwheels all he wants, but unless he enters the neutral zone, he is not offsides. If that were not the case, then anytime a defense simulates or fakes a blitz, then all the O-linemen have to do is move and say they were forced to move and that the defense was offsides.
If the dlineman enters the neutral zone and the offensive player moves while he is in at least the neutral zone then it's neutral zone infraction On the defense.
If the offensive player moves too late and the dlineman gets back out of the neutral zone, then they call it false start on the offense.
If the defensive player just blows by everybody it's blown dead and offsides unabated to the QB is called.
If the dlineman just gets an early jump but the olineman still is able to get between him and the QB then the play is allowed to continue in what is called a "free play". Where they at least have the upcoming penalty to fall back on.