Going into this tie, I would say that Barcelona have a 60 per cent chance of going through against Chelsea, maybe even 65 per cent.
But Chelsea have shown they are capable of winning matches in which they are not the favourite but putting psychological and physical pressure on their opponents at home.
Players like Didier Drogba, John Terry and Frank Lampard have plenty of experience in this competition. It won't be so easy for Barcelona. They will be aware of the threat Chelsea pose.
For the players involved when they last met at Stamford Bridge in 2009, that match will stay in their minds for the rest of their careers, but it should not have any bearing on the result this time around. What will decide the winner is which team deals with the issues of the here and now better.
Chelsea know what to expect when Barcelona come to their stadium, and they must be prepared to see their opponents have as much as 70 per cent possession of the ball on their own turf.
That works out at around 18 minutes of the 90 in which they will have the ball, and they must use those 18 minutes as effectively as possible by asking questions of Barca's defence.
Chelsea could be well suited to that, given they like to attack in such a direct manner. They will also hope to dominate Barca at free-kicks and corners. Drogba will be key to giving Barca a difficult night when Chelsea take the aerial route against them.
Chelsea will be hoping that John Terry can play in this game despite nursing a rib injury. He is vital for them in this type of game, when Chelsea's defence needs to stay focused for the whole 90 minutes.
Chelsea v Barcelona previews: