United saw their unbeaten start to the season come to an end in shock fashion as goals from Aaron Mooy and Laurent Depoitre condemned them to defeat, with Marcus Rashford's reply all the visitors could muster at the John Smith's Stadium.
"They beat us on attitude. When I lose matches I like to lose because the opponent was better than us, had more quality than us. When you lose a football match because of attitude, that is really bad," he told reporters.
"I heard Ander Herrera in the flash interviews saying the attitude and desire was poor....Oh my God. When a player says that, when a player feels that, I think they should all go to the press conference and explain why because I cannot explain that. I don't even remember a friendly match where our attitude was so poor.
"I feel really disappointed and if I was a Manchester United supporter, not a manager, I would be really disappointed. You like 'individualisation' of the mistake and the defeat. I think it is very unfair. If you play an amazing game and lose to an individual mistake, yes, you point the finger. That is not the case. In the first half I was waiting for it. It was [Juan] Mata and Victor [Lindelof]. It could be another one because the attitude was really poor."
United will look to return to winning ways when they take on Swansea City in the EFL Cup on Tuesday.