yes With Hojlund being absent for 3 to 5 weeks this will be a big loss for Manchester United who are currently in the hunt for 4th place in the standings. In my opinion Erik Ten Hag will again lose stability in his attack line. They will face Manchester City in the 28th match which will certainly only make the situation worse. Even if it is maximized there is still a possibility that Manchester United can at least finish in the top 6 and play in the European League.
3-5 weeks?
It is a really long time period for the Red Devils. They are really unlucky about his injury. As far as I remember he was injured for a while when he first arrived here as well. The fans would hope to see him healthier than this. Especially while there is a big improvement in his performance the team need him a lot. 
About the Manchester City game yeah his absence would make things worse in the attacking line. However I think with or without him the Red Devils would lose this game anyway. I appreciate the way they improved their form recently but this game is still very difficult.
The good thing is now if some players were able being placed as a striker to replace him. Manchester united has other choice to put martial in the squad but ten hag seems not even interesting to do that. I meant he may prefer to put his trusted guy like rashford to play as a striker instead of martial.
Martial will still be benched without know when he will be playing for the main squad again. It surprises me to hear that caused by hojlund was still going very well in the last match. It relaly surprises me to hear that holund was fucking injury and he will be out for weeks from the main squad.
Unbelievable news but since he has also getting injured in the past and this situation looks common. The main problem pwned by hojlund if he was injury prone. It can be seen from how he was trying so hard to perform better but it was also costing a lot.
Hojlund paid his good performance with injury caused by he was playing aggresively. This sounds bad fior the team but this can't be avoided too. Let's put our trust to the team that is still hardly working on finding the good solution for hojlund's injury.
Many people are also feeling so bad after they heard this news. I could not even believe it caused by he was still doing fine in the match against brentford.