Leeds will have some 9,000 supporters at the game and most of them still have some idea that there is intense rivalry between the two clubs.
Superintendent John Graves, says they are ready to tackle any trouble.
He said: "The big game of the decade for Leeds supporters will be coming to Old Trafford and so we do expect a lot of supporters not to want to miss this opportunity.
"Both clubs have great support and both have suffered loss and tragedy, but it would be wrong for a small minority of idiots to use those as an opportunity to incite violence and disorder.
"We are not going to allow a small minority to spoil it for the vast majority of decent law- abiding fans that want to come here and enjoy the occasion."