Manchester United is in big trouble, it seems difficult for them to get out of their downturn. Not only is the crisis of players experiencing injuries but the crisis of self-confidence is also another problem that must be considered.
Yes, Erik Ten Hag's mistake was when he threw De Gea out of the squad and replaced him with Onana. Onana was brave enough to be brought to Old Trafford because of his impressive performance with Inter, but unfortunately for United he always made mistakes that were detrimental to his team. Not only Onana, several other players must also be evaluated for the good of the team. I don't know how long Erik Ten Hag will stay at Old Trafford, if he doesn't get better maybe he will soon be asked to leave because the club has spent a lot of money to build the squad.
After a series of bad results they have received since the start of the season, of course this has had a big impact on the team's self-confidence and the defeat against Galatasaray made things even worse.
And indeed Erik Ten Hag doesn't have many options to get the Manchester United team out of its current problems because many Manchester United players are injured, but no one else can be responsible for what is happening now except the coach.
However, I don't think this is a fault with Onana or Tenhag who prefers Onana over De Gea because all the Manchester United players can't work well and the coach's tactics can't go according to plan because of the limited players they have.
It is very difficult for Manchester United to recover, and now they are slumped at the bottom of the group standings after experiencing 2 defeats in the 2 UCL matches they have played.