I could hardly bear to watch Leeds beat Manchester United at Old Trafford, knowing what the fixture means to both sets of supporters.
Simon Grayson's side are having a great season, and came into the match full of confidence. It was the biggest game of their season and it showed.
They deserved to beat a United team that never really got out of the blocks, and their names will go down in the history of the club. It is what the FA Cup is all about; it always seems to produce an upset.
I think the United team did not have enough players who have played against Leeds and know the significance of the rivalry.
I did not appreciate it fully when I moved to Old Trafford in 1991 until I had played and experienced the atmosphere.
Players like Darron Gibson, Danny Welbeck and Gabriel Obertan will not be able to remember Leeds as a major force in English football - it was the perfect opportunity to start Ryan Giggs and Paul Scholes who know what playing against Leeds is all about.
United needed to get their noses in front and take control of the game, but they did not do so and were simply not good enough.
Sir Alex Ferguson gave a fairly blunt assessment of his team's performance afterwards and he will be extremely concerned at their failings both at the front and the back.
Rio Ferdinand has not played for more than two months and there is no knowing when he will return, while Nemanja Vidic has suffered yet another mysterious injury.
Wes Brown thought he was a substitute but got thrown straight in and it showed: he was not properly prepared mentally and was given a torrid time by Jermaine Beckford.
Up front, it doesn't take a genius to see they are missing Cristiano Ronaldo and Carlos Tevez. United needed the likes of Dimitar Berbatov and Michael Owen to step up this season and they simply haven't done it.
If Ronaldo had been playing, he would probably have scored. If he hadn't scored, he would have set up a goal. And if he hadn't done that, he would still have had two players marking him.
Ronaldo makes things happen, whereas Owen and Berbatov need things put on a plate for them - and it puts too much strain on Wayne Rooney.
It is nigh-on impossible to replace Ronaldo, but I think the loss of Tevez could be offset by someone like Hulk at Porto.
I like what I have seen of the Brazilian, and he would certainly add some pace and creativity up front.
Tevez always gave 100 per cent, and you could rely on his energy and work-rate even when he was not scoring - Hulk looks a similar player.
The Argentine has a chance to show United what they are missing on Wednesday in a Carling Cup semi-final derby that takes on huge significance following the Leeds debacle.
Sir Alex has promised to ring the changes, and you can be sure United will not take quite such a complacent approach to the City encounter.
- Cristiano Ronaldo