Do we have a chance? Obviously. We're like the best defensive team in club football and they are the best offensive team around, this is typical fire vs ice situation. What's better is both teams can take care of the other side of the game too. While we're not a wonderful offensive machine, we can get goals. While they aren't the best defensive team, they don't really concede much.
For me how much of a chance we have will be determined by our Max's tactics. If he plays the right team, I don't see them creating much and I'd back us to sneak in a goal or 2 and closing up shop. If we play the wrong set up, I have a feeling we're going to be in for a long night. Barca is very good at being front runners and chasing the game against them can lead to things getting ugly real fast. They do have the single most decisive player in world football.
Barca play a simple formation. A 4-3-3 with messi as some sort of right wing cum classic 10. We should know all about those since we had 2 of the greatest ever classic 10's to ever play(Platini and Baggio). Handling him is going to be pivotal but if you've watched enough of him you'd know that if things aren't going his teams way, he tends to disappear from matches. The best way to do that will obviously be to neutralise his supply and make sure his accounted for. Neutralising the supply would be making sure that someone like iniesta doesn't have a big game.
Here's what I would do to give us the best chance of winning. He has to leave pirlo on the bench IMO. Pirlo's lack of athleticism is at a point where he hurts us more than aid us nowadays. Our pressing game falls apart when he's on the pitch as defensively he's such a big liability. He's not going to win much loose balls or put anyone under pressure. He's not going to cover our fullbacks or defend well into the box if they penetrate us. Essentially we need Marchisio there who can do all that. While he doesn't have the pirlo passing his defending at the base of midfield is wonderful. Plus he's not all that bad with the ball at his feet.
Another adjustment I'd like to see us make is to play vidal on the left instead of the right hand side of our diamond. Why? That's messi's area and controlling him will be essential. Pogba is a fantastic footballer but defensively isn't on vidal's level. Evra is an occupational hazard but him being beat on the inside has to be accounted for by the midfielder covering for him. Doubt even at this age that evra is gonna get beat much on the outside. Another thing is Pogba on the right would need to play deeper than he usually does, and given that he's the most technically gifted midfielder we have that's also going to be important. We need him to use his passing range to beat the press and his dribbling to play out from the back. Another thing is that, that side is Iniesta territory and we've seen Pogba handle him well while playing for france.
We need our attackers to get the job done when the opportunity arises. Pereyra vs Busquets on the counter could be useful to us.