Eric Hag wouldn't have any other choice than to get an alternative for Anthony's position. It is a pity that this is happenings during this time that Man United is in a critical state with poor performance from the club. The transfer window is closed now maybe by next year when the window is open Eric Hag can make a replacement for Anthony. I don't think that Man United will go far this season because they are not in a good form since they are struggling with their matches. The champions league would be a mess to them because they don't have the quality it takes to perform well in the league. I just hope that Anthony should be able to iron out the allegations on him.
Antony is indeed the first choice in the right side position but Man United still has alternatives if Antony cannot play. There are still Garnacho and Pellistri who can fill that position and there is also Mason Mount who can also play on the right side, it's just that he is still injured, so the most likely option that Man United has is to play Pellistri or Garnacho.
The problems that Antony is currently facing may affect Man United's performance but I think there are other serious problems that need to be prioritized first. Man United's defense is not doing well, while Ten Hag doesn't have many options that can be used as a solution.