BBC Sport is looking back at 50 iconic FA Cup goals in the build-up to the first round proper, which takes place in November.
"You must always play to the whistle." That's one of the first lessons you are taught as a young footballer - but one which experienced Manchester United keeper Fabien Barthez did not heed in January 2001.
And it proved costly as the Premier League champions were surprisingly dumped out in the fourth round of the FA Cup by West Ham.
The World Cup-winning Frenchman audaciously attempted to psyche out Paolo Di Canio as the Hammers striker evaded the home defence's offside trap to race on to Frederic Kanoute's throughball.
Barthez, to the surprise of Old Trafford, stood motionless with his right arm in the air in an effort to make Di Canio think he was offside.
But the maverick Italian was not duped. He did play to the whistle, expertly firing under Barthez - whose despairing dive was too late - with the outside of his right boot.
The 76th-minute strike proved to be the winner in a 1-0 away success and saw the east London side earn their first win at Old Trafford since 1986.