The Red Devils suffered a late 1-0 loss at Lerkendal Stadion after Noah Holm’s 93rd-minute winner.
An underwhelming performance in their first pre-season game was in stark contrast to their last outing before that, a 2-1 victory over rivals Manchester City in the FA Cup final.
Rosenborg were denied by the woodwork on four separate occasions while attempting 22 shots to United’s meagre five.
Ten Hag started the likes of Casemiro, Jonny Evans, Marcus Rashford, Aaron Wan-Bissaka and Mason Mount, leaving the United boss somewhat furious with their efforts in Trondheim.
“The result is not secondary. We play pre-season but at Manchester United, there’s a standard,” said Ten Hag to MUTV after the game.
“You win games. Definitely, you don’t lose games. If you can’t win, don’t lose the game as we did at the end, the last second of the game.
“The performance is more important. The performance was below standard.”
Radek Vitek, United’s 20-year-old goalkeeper, was forced into seven saves in a one-sided pre-season meeting as the only Red Devils player to impress.
“Let’s say he got the opportunity from the team to make some very good saves because our performance as a team is by far not good enough,” Ten Hag responded when asked about Vitek’s showing.
“I have seen this is not the standard for top football. Top football, you have to achieve much higher standards. It starts with any individual, make sure you are fit.
“I know we can’t be match fit in this moment, therefore, you need these games. I know we are playing an opponent who are in their league, they have a much higher fitness level.
“But still we are Man Utd and players and teams from Man Utd must perform better.”
Ten Hag’s only credit from the game was placed on the youngsters who came on at half-time in wholesale changes.
“They always listen, they try to transfer. We didn’t succeed today,” the Dutchman said of his younger players.
“But the attitude, they want to transfer the coaching play model, they are always willing to do it. But it is clear today we didn’t transfer it to the pitch.”