Arsenal have played three times against Barcelona over the last seven or eight years. I think that they still have the best technical skills, but they have lost something.
They are more vulnerable in defence and I know PSG have the offensive ability to take advantage of this little vulnerability that Barca haven't had in previous seasons.
If you stop Lionel Messi do you stop Barcelona? Probably, because he is involved in 60-70 per cent of Barca's goals, but the other challenge is also to prevent Barcelona's players from giving him service.
Blaise Matuidi will have a big responsibility in this respect, and it's fortunate he was conditioned to the Spanish way of playing at Stade de France for the recent international match.
It will be the same match configuration on Tuesday night: possession in favour of the opponent, with Paris having to construct decisive counter-attacks.
However, I think Barcelona are currently more vulnerable than the Spanish team. Arbeloa, Monreal and Sergio Ramos were all excellent against les Bleus and they won't be in the Barcelona's defence. Barcelona are currently less solid than the Spanish national team.
Zlatan Ibrahimovic faces his former side and his time at Barcelona was not a success because during that period there were other players who could play in the same position. Too much competition 'kills' the competitor for one reason: it puts an end to the player's self-confidence.
Maybe there was also a young kernel of players, a core with Messi and Iniesta ... so there was a solidarity around them.
Has his personality prevented him from going to have an even greater career? I don't know ... this issue might also be a strength for him.
When he doesn't score, people criticise his behaviour as arrogant. But on the other hand, he probably needs that to perform, to feel strong. Also, one should accept that he validates this arrogance with his performances on the field.
He is a player who has won eight or nine different national titles and, believe me, there is no chance, no luck that can account for this - it is even more significant than winning the Champions League.
Everywhere he goes, he makes his team win and he will do it again this year. So it's not only his skill and his talent but also this consistency of success.
As for Bayern Munich v Juventus, I'm sure it will be a very balanced match. Juventus are a very solid team, especially in defence, and are playing with confidence on the counter-attack.
Bayern Munich are a physical machine, a steamroller. They are not always very creative, it's true, but terribly effective. With Ribery in great shape, I would give a little advantage to Munich.