Anything can happen when it comes to football match, with the way we are hyping Barcelona like this as if they haven't been defeated by a smaller team before, when it comes to finals like this, lets just take it form the recent example of what happened between Inter Milan and PSG.
As most people have the expectation that Inter will not take it likely on PSG because going by tier previous performance from the league, they have remained outstanding, but to the greatest surprise of us all, PSG was able to score 5 goals in the history of UEFA champions League final and Inter couldn't afford to score a single one, don't be surprised Barcelona could have been in a more worse situation as these.
In as much as I know and will want to agree with you that in the game of soccer anything is possible, I will also want you to understand and know that PSG is not a small team or ordinary team, if we should look at the players they got, you'll want to agree with me on this, you can say that inter got more experience than them in the affairs concerning the UEFA champions league but for the example you gave which I feel that you're referring them as a small team I don't think that's right unless I didn't get your instance correctly.
Yea Barcelona has lost to perceived lower teams that are not their equals before, it is in their history but the point some of us were trying to make on the discussion at hand is that it would've been a different game if Barcelona were in the picture considering the fact that both teams have a similar play pattern in the football field, so that's the point, I hope you understand me.