Manchester United have had a really good run in the recent times and they are on a winning streak of four games now. As their Crystal Palace game has been postponed they are going to face Leeds in Old Trafford next week. This break might be good for the team to stay focused on their road. They are doing very well recently in the league and they need to continue like this. The result they got in the Europa League shouldn't be any disturbance for them. Their priority is the Premier League this season.
It's true, even though they lost in the Europa League it shouldn't bring them down mentally. And the defeat at that time was because some of the players who used to be the main players were not sent down by Ten Hag. I think he's trying to see what his team looks like when they lose some players. They can use this time lag to create chemistry within the team.