Without Casemiro, Manchester United will lose balance in midfield. Casemiro absence is a loss for Manchester United, considering that Manchester United's winning percentage is quite high when Casemiro appears.
This has made it difficult for Manchester United to find a suitable replacement for him, but I believe Sabitzer, McTominay, or Fred are capable of replacing Casemiro role in midfield even if they don't completely cover the midfield properly. Erik Ten Hag knows what he is doing and will handle it well.
but their opponent is Sevilla, they have been quite poor this season, although they have finally started to play quite well in a few games. but Sevilla is still not playing consistently. maybe they will surprise in the Europa League.
even without Casemiro, Man United is expected to be able to win. especially with their performance which is quite improved in the Premier League at this time. Let's just see how Sevilla survives Ten Hag's strategy in the first leg.