AIDY BOOTHROYD will lead his side out at Villa Park tomorrow (Saturday) admitting that a Watford victory in the FA Cup semi-final against Manchester United would represent a "major shock beyond belief".

The Watford manager was at Old Trafford on Tuesday to watch United sweep aside AS Roma with a European masterclass and, in the process, extinguish any optimism the Hornets had built up following Monday's uplifting win over Portsmouth.

Victory over treble-chasing United would surely represent the biggest shock in the competition's illustrious history, eclipsing Wimbledon's 1988 Cup Final win over Liverpool, Crystal Palace upsetting Liverpool in the 1990 semi-final and Wrexham's memorable third round giant-killing of Arsenal in 1992.

Indeed, Watford's chances have been reflected in the fact they have failed to sell their ticket allocation, selling just over 15,000 of the 17,806 they were handed by the Football Association.

"There have been shocks before but this would be a major shock beyond belief - it would be up there with man landing on the moon," said the Watford manager.

"A man has done that so anything is possible. We know it's going to be an unbelievably hard task but we'll be positive. It's been done before and we'll be talking about upsets in all sports before the game. There is always a chance and if we prepare correctly and all our players are at ten out of ten then you never know."

Boothroyd was joined at the Theatre of Dreams by Dick Bate, the first-team coach, and together they have formulated a game-plan that he hopes will, at the very least, make things difficult for the Premiership leaders.

"We'll prepare as thoroughly as we can," Boothroyd said. "We've got to make sure we are right. We've got a game-plan for containing and threatening them and make sure when we get chances - because we will get chances - we take them. We will go and enjoy the game, there is nothing else you can do."

Boothroyd got it badly wrong the last time the two sides met - deploying ten men behind the ball and waiting for United to break them down. The Red Devils obliged, scoring four and creating a hatful more. The key, he agrees, is marrying attack and defence.

"We have tried defending deep against them and we've tried pressing them and neither worked," he said. "If you go out gung-ho against United then you will get punished. But if you show them too much respect and you camp yourselves in the six-yard box then you are going to get done because it will only be a matter of time before they score. We have got a game-plan and will try and put it into action."