Trapping the offense

You begin by having two defensive players and one offensive player. The defensive players set up one yard away from the offense with their inside feet slightly inside the feet of the offense.  The outside feet are both outside the feet of the offense and forward toward the offense.  The offense tries to walk by, through or around the defense.  The defense prevents this walking by moving with the offense, keeping the offense in the same relative position between the two defensive players.  Block the offense if they try to go around or through the defense.  Each drill lasts 15 seconds with each player changing positions three times.