Before you start criticizing, look at the lineup Manchester United played. Apart from Rashford and Casemiro, I don’t see who could stand up to Rosenborg. This is a friendly match in which the coach wants to see what the young players are capable of, the result in such matches is of secondary importance. Now, probably after the Euro, the players will receive a short vacation after which preparations for the new season will begin, then it will be possible to evaluate the team’s results.
Friendly matches are always a special concern for coaches regarding young players and in this match where Erik Ten Hag fielded young players against Rosenborg, the final result was that Manchester United lost with a score of 1-0. So, if you look at it from a game perspective, of course Manchester United young players still seem to have difficulty keeping up with Rosenborg game. For me, this defeat is a big evaluation for Erik ten Hag in the next friendly match because with Manchester United's big name, of course this defeat is very embarrassing, especially since the team they are facing is a weak team.
On the other hand, the transfer market is still ongoing and of course Manchester United management must take advantage of it to recruit several more players to strengthen the squad to be stronger for this season.