Of course this is a bad blow for Man United, Casemiro's injury means that the list of injured Man United players has increased. Losing Casemiro is certainly detrimental to Man United because he is an important player in Man United's midfield, plus he is currently the top scorer so far with four goals in all competitions.
With so many players injured, Erik Ten Hag has to think smart about how to play players when facing Fulham next week. Because this match really determines the fate of Erik Tag Hag's future at Man United, Fulham is not a strong team. I think Erik tag hag should make the most of his opportunities.
Eric Ten Hag will need to use all of his coaching strategy and skills to help his club outperform Fulham this weekend. Fulham shouldn't be a difficult team for them to beat, but with the present squad and issues that Manchester United is experiencing, even Fulham will want to take advantage of them in order to defeat them, which could jeopardise Eric Ten Hag's position. Although when you genuinely want something so badly, you're expected to provide results even in your worst state, so he has no actual reason not to win this match, especially because it's an inferior team that they can easily win on a normal day.