Barcelona are not unbeatable.
That is the one thing everybody seems to be overlooking. We saw Inter do it last season, we have seen Arsenal do it this season and Real Madrid do it in a big, one-off cup final, and that is what Manchester United have to remember.
They are without doubt the most fantastic football side I have seen in my lifetime and they do have an aura about them which most teams cannot handle, but they are by no means perfect.
Look at Roger Federer, look at Tiger Woods; we all thought these guys would never lose because they were that good, but we've seen they can be beaten - and so can Barca.
United have to believe that. They will know they have enough match-winners of their own at Wembley and if you are looking at a team to upset the odds on the biggest stage of all, then who better?
Mind you, it is going to be very, very difficult. The biggest problem they are going to have is spending long periods of the game without the ball. That will happen against Barca and they will get tired and frustrated and at times, they will end up chasing their tails. It is something United do not have to deal with in the Premier League and that is my biggest worry.
It's impossible to say - other than praying for devine intervention - how you stop Lionel Messi, Xavi, Andres Iniesta, Pedro and David Villa and in a way that's no bad thing, because I do think the biggest thing United have to focus on is what they do when they're in possession.
When you're playing Barcelona, you have to keep the ball; you cannot turn it over cheaply because they will make you pay. United will know they are not going to dominate, so they will make sure they do whatever they can to hurt Barca whenever they can.
That is why I think we will see Ryan Giggs and Michael Carrick start in the middle. They are both great technicians, great passers of the ball and that is going to be needed. There is talk of Darren Fletcher coming in to man-mark Messi, but I can't see it. For a start he has not played enough football for a big game like this and secondly, United need their best passers.
We might see Ji-Sung Park join them in a middle three with Antonio Valencia on the right, maybe Wayne Rooney on the left, and Chicharito up front. But then I am not so sure asking Rooney to play out on the left is the best idea in such a big game and not sure it sends out the right signal. United want him where he likes to play; which could be up top on his own or in behind Xavier Hernandez.
I am not about to second guess Sir Alex Ferguson but I just think, knowing what a master of psychology he is, that he will want a positive line-up and a positive approach from his team. It might be that he goes 4-4-2 and says 'we're Manchester United, this is what we do best'.
I have been watching the 2009 final back and United actually started off really well. They pressed Barcelona brilliantly, high up the pitch, forced errors, corners and could've been 1-0 up. But then one small mistake from Carrick after nine minutes, they're 1-0 down and from then on, it's an impossible task.
They will have learned from that and they will know that every single one of them has to be on their game, for every second of every minute. Switch off against these players and before you know it, they are in on goal. Rio Ferdinand and Nemankja Vidic will have the hardest job, not just because of the players they are up against, but because for a lot of the time they will have no-one to mark.
Messi, Villa and Pedro will all move about across that front line and they will all drop deep, creating space for someone else to run into. Every single Manchester United player has to watch the runners; they have to have the confidence to be able to pass someone on to the next man, because if you follow the ball, or get attracted to Messi, it leaves you wide open. That is what Barcelona do. They pass you to bits, then wait for you to tire or switch off and then they pounce. It is a very swift end to a very slow death.
Then you have to worry about Dani Alves down the right and I have to say that is another area of concern. I am not sure, defensively, Patrice Evra has had his best season and with Villa, Pedro, Messi and Alves all capable of attacking down his side, he will need some help - which might fall to Park in a left-sided role.
But dealing with Barcelona is the one question the whole of football is looking for the answer to. Do you attack them or do you try and keep your shape, frustrate them? Again, Arsenal beat them by having a go at The Emirates and maybe Sir Alex will think that is his best bet.
This is also a United side that is flying. They have eased through this competition, have not conceded an away goal and they are coming off the back of winning the Premier League. You can easily turn it round and say Barcelona won't have faced anyone like them this season. They are a side that loves winning and is geared up for winning.
And I don't subscribe to this idea that this United side is not great, either. They are a a great team, maybe not with great inviduals. But Pep Guardiola knows they have some world-class players in their squad; whether he pays them special attention or not remains to be seen, because that's not their way.
There's no doubt United have the players, and the bench, to hurt a side that can be got at defensively. We don't know what state Carles Puyol is in, we don't know if we're going to see Javier Mascherano in central defence; like I say, they are not invincible and by no means perfect.
My honest opinion is that Barcelona will be too good on the day. But I wouldn't be the slightest bit surprised if Manchester United won this, I really wouldn't.
I am going for Barcelona to win 2-1. It would be great to see an English team win the Champions League but in all honesty, as a football fan, I don't mind either way. We are talking about the two biggest clubs in Europe, if not the world, and the two best sides right now, playing at Wembley in the biggest club game there is. What more can any fan ask for? I really do hope it's a great game and I think if Sir Alex has a go - and I have a feeling he will - it will be worthy of the occasion. If United do pull it off they are going to have to be right on their game all night long and they are going to have to ride their luck as well, and we all know they've done it before in big games.
Pedro (Barcelona) and Wayne Rooney (Man Utd) - Everyone is talking about Messi but for me, Pedro is the one that can do real damage if you take your eye off him. He makes so many clever runs and he is pretty direct when he's in the box. He is a very clinical finisher too and if they get caught up watching Messi, Villa and Iniesta, he will sneak up and hit United where it hurts. As for Rooney, United need him to have a big game, more than Barcelona need Messi. If he plays behind Hernandez he will have a big say, but if he does play him out wide, I am not sure we will see him firing on all cylinders. He will want to play down the middle, he will want to get on the ball, not spend the night chasing Alves. And he will want a big, big performance. If United are going to nick this, they will need just that from Rooney.
Who will win the UEFA Champions League?