Christian Erikson's injury is a big blow to Manchester United, even as Barcelona are without Dembele too, but it won't really change the outcome of the match if two of them don't make it to the match squad for that day, Manchester United have players capable of replacing Christian Erikson and Barcelona have players to replace Dembele and that game Wil come down to the mangers tactics, it will be a tactical battle between the two teams and the best thing will come out victorious.
Any team that wins the first leg Wil take that advantage into the second leg and progress, so I think the first leg will be the decided of the tie .
Eriksen's injury is a separate problem for United, because their stock of midfielders is very limited at the moment. although it is reported United are trying to sign a new midfielder before the transfer window closes. however, Eriksen's absence will have a major impact on the team's overall performance, especially to help the front lines when building attacks. as for the other midfielders, not an ideal choice for Ten Hag especially Fred who is more of a defensive midfielder. Ten Hag had little choice but to sign a replacement before the transfer window closed.
Meanwhile, Barcelona are expected to miss Dembele in the coming weeks. at least, he will be absent in the playoffs later. however, Xavi still had other options and changed their tactics and formation schemes. but what is certain, these two coaches will prepare their troops to perform as optimally as possible when this match is held.