As a result of this Barcelona's away match, the Barcelona team would not have faced too many problems. Because the Manchester United team is not very strong at home. However, several key Barcelona players will not make the squad. Barcelona's main strength this season has been their midfield. Of course, without players like Dembele and Gavi in the squad, Barcelona will face a huge problem. But if Lewandowski performs well, Barcelona's chances of winning are high. We don't see a better performance from Lewandowski in the last match. And in a high-voltage match, the team expects a lot from an experienced player like Lewandowski.
I think there is going to be a bit more story to this game as well. United might be bought by Qatari person very soon, not that it would be official until the game starts that much is true but it could be unofficially done deal, and if that happens then we are talking about a whole new ownership of the club. In that situation there will be an added story, basically de facto first game of the new owner, once again not officially but it could be handshake deal done by that point.
This could have two responses by the team, either United will play amazingly so that they would keep their positions, or they will play even worse because they would worry about their positions in the future.