Louis van Gaal questioned the will to win of his Manchester United players after he watched in shock as they slumped to a 3-0 defeat at Arsenal.

United conceded all of the goals in the first 19 minutes and Van Gaal complained about their failure to execute his gameplan, together with their lack of aggression. He said that he had made his feelings known to them at half-time and full-time.

“I didn’t expect that,” Van Gaal said. “I was surprised – not performing to our gameplan, not the will to win. I have not seen that, when you are top of the league [as United were at the beginning of the weekend]. So I was surprised, amazed – maybe that is a better word.

“When you give a team like Arsenal so much space to play football, then you know you will lose. We prepared ourselves to play more compact and not losing our aggression, so it was amazing for me. I am very disappointed.”

Van Gaal said that he had no explanation for what had happened at the outset, when Arsenal tore through his team, with Alexis Sánchez scoring either side of Mesut Özil’s goal. “I don’t know why it happened,” Van Gaal said. “I put the question at half-time and after the match. It is difficult for the players to answer at the moment, because they are all in an emotional moment. We have lost, and lost in a way that you cannot lose when you are top of the league.

“The problems did not start at the back, they started in midfield. Their midfield players, especially Cazorla and Özil, had too much time and space. We also had space behind our defence. When you always put the pressure on, they cannot make their passes so easily. That was our problem in the first half.

“They were not aggressive. And you have to do it not only with the two in midfield but as a team. You have to be more compact. You need aggression at the moment you have a duel and Arsenal were much more aggressive.”

Van Gaal said that his frustration was compounded by the fact that most of his players would now depart for international duty, with some of them flying straight out of London, and there would be no time for him to work on restoring the collective confidence before the trip to Everton on Saturday week. Arsène Wenger, too, had reason to bemoan the international fixtures. Sánchez limped off towards the end with a groin problem but he will join up with Chile before their World Cup qualifiers at home to Brazil on Thursday night and away to Peru the following Tuesday night.

“He has a little groin problem and, unfortunately, he goes to Chile,” the Arsenal manager said. “You cannot stop him from going to Chile. He loves so much to play for his country and they play against Brazil and in Peru. He will not want to miss the Brazil game. I hope he will come back in good shape.”

Wenger was delighted with Arsenal’s performance, which represented a ”strong and united” response to Tuesday’s 3-2 home loss to Olympiakos in the Champions League. He felt that all of his players had played well, particularly Theo Walcott, who set up the second and third goals. Wenger described it as ”certainly one of Walcott’s best games as a No9.”

Arsenal’s manager, Arsène Wenger, praised his team’s strong response to their Champions League defeat but Manchester United’s Louis van Gaal was understandably disappointed Guardian

Wenger said: “We were convincing and it gives a strong answer to all the questions that were raised during the week. What you want is a strong response when you have a big disappointment. We have to put it all in perspective and focus on what is important – it’s us and not too much on what was said.

”The pressure on any disappointment is massive today, it makes it a bit more difficult to deal with and we did it well. To win in a big game is always a statement and we are in it [the title race]. I hope that the result will give us belief and ambition for fight for it.”