The tie must be seen as the stand-out fixture of the round, but it is about the meeting of two of the biggest clubs in Europe - David Beckham as an individual doesn't really come into it.
There are plenty of other players who have left United and faced them for their new clubs, but there was never the hype that there is about Beckham at the moment. It might make a nice story for him personally, but from a footballing perspective it is an irrelevance.
Right now he is only on the fringes of the first team, after disappointing in the recent derby match and only coming on as a substitute in Milan's last two games. The return from injury of Pato and the January signing of Mancini have relegated him to the bench.
Leonardo may not see the former England captain as the man to help them through this tie, and I would be very surprised to see him start at the San Siro.
The Milan boss knows that an ageing Beckham will not be sharp enough in midfield when his team don't have the ball, and even when they do he will be hounded by the likes of Darren Fletcher and Park Ji-sung, players who cover ground very quickly in the centre of the park.
Leonardo would do well to follow the example of Alex Ferguson by not letting sentiment over Beckham cloud his judgement, as it could cost him and Milan dearly. Milan fans won't be interested in his reunion with a team he last played for almost seven years ago, and they could turn on the Brazilian coach if he panders to the hype.
Ferguson is probably hoping that Beckham does feature, as that could play right into his hands.
Not many players are as vocal about the club they supported as a boy as Beckham. Usually, when you turn professional, you put aside your childhood allegiances. I supported Tottenham as a boy but I quickly grew out of following them once I started playing professionally, and I think that is true of the vast majority of players.
Beckham has spoken a lot about bringing his whole family up to Old Trafford for the second leg, but he should really be restricting his talking to the matter in hand, namely getting himself back in the team and helping them reach the next round.
United travel to Milan having lost on each of their previous four meetings. It will be difficult for them to break that dismal run, especially at the San Siro, where I have been to see them lose twice.
Although Milan have been usurped by neighbours Inter in recent years, they have managed to maintain their exceptional European pedigree.
Ronaldinho has been in outstanding form this season, playing some of his best football since he was last crowned World Player of the Year. He is sure to cause problems for whoever plays at right-back for United, whether it be veteran Gary Neville or an inexperienced and possibly awestruck Rafael.
However, if Alex Ferguson can get his team playing at a high tempo against an ageing Milan side to the effect that saw them tear through Arsenal recently, then they have a good chance of outscoring them and ending their hoodoo.
- David Beckham
- Manchester United