Manchester United manager Louis van Gaal says he was surprised by the way his side lost at the Emirates against Arsenal.
The Red Devils conceded three goals in the first twenty minutes of the game and it could have been worse had the Gunners taken their chances in the second half of the game.
The defeat means Manchester City stay top ahead of the international break with United in second place on 16 points.
"I didn't expect that. I was surprised," van Gaal told reporters.
"No performing our game-plan, no will to win. We were top of the league so I was surprised – maybe 'amazed' is a better word. When you give a team like Arsenal so much space to play football, you know you shall lose.
"We have prepared ourselves in that way, to play more compact but not to lose our aggression. It was amazing for me and very disappointing. The players are in an emotional moment because we have lost. We have lost in a way you cannot lose when you are top of the league. You cannot start like that.
"The [Arsenal] midfielders, especially [Santi] Cazorla and [Mesut] Ozil, had too much space and they have the quality to make the most of it. We lost every duel, every second ball.
"We were not tight on their midfielders, and they can play because they are a fantastic team. We have to do better as a team. The defence starts with the attacker. We have to be more compact against teams like Barcelona, PSG and Arsenal, but with the same aggression."