I don't think Barcelona will face too many problems in Dembele's absence. Xavi's match strategy is excellent. So Barcelona will be able to play well even in Dembele's absence. Raphinha will also play as Dembele's replacement. Raphinha may not be as experienced as Dembele but he is a talented enough player. Raphinha looks set to play well in Dembele's absence. Raphinha's performance was good in the last match as well.
Several players in Manchester United's squad will not be able to play due to injuries. And Casimero will miss a match due to a red card. Looking forward to seeing how Ten Hag will strategize without so many key players.
Barcelona is a team that is in a more comfortable position compared to Manchester united, they are advancing in the league as they wish, while their closest rivals lose points, they continue to progress by opening up the difference in points. The absence of Dembele does not cause much trouble to Xavi's game, at least there is an alternative that can fill his place. On the one hand, Manchester has to think about the league side, they have a lot of injuries and it will be difficult to replace those players.
Barcelona may be great at league games, but that doesn't mean they are better than United, and even if it does mean they are better than United, they were better than Frankfurt last year as well, but they lost to them all the same, so a worse team could still a better team. This is why I believe that it is quite important to focus on what could be done and how they could they win if they are a better team.
I know it is going to be a tough game for both teams, they are both doing fine and they will want to both win the game as well. It is great for us, because it means that we are going to get to watch two great teams fight each other and it will be awesome to watch.