Manager Arsene Wenger said a poor start sabotaged Arsenal's hopes of extending a 12-match home winning run in the Premier League as they went down 3-1 to Manchester United on Saturday.
There was much to admire in Arsenal's attacking play but they never fully recovered after defensive sloppiness allowed Antonio Valencia and Jesse Lingard to put a livewire United side 2-0 up after 11 minutes.
Alexandre Lacazette replied early in the second half but Lingard struck again on the break just past the hour as Arsenal suffered their first home defeat in the league since January.
Their winning sequence, their best at home for 12 years, began in April against West Ham United.
"I think we didn't start well at all at the back and we are guilty of that," Wenger, who has won only twice in 19 clashes with United's manager Jose Mourinho, told reporters.
"Psychologically it was a big blow to go 2-0 down so early on -- especially at home. We were too on the edge mentally maybe -- you cannot be in a game like that.
"We played well but there is nothing more frustrating than when you have that quality of performance and nothing to show for it at the end. The attitude was impeccable until the end. But you cannot make the mistakes we made at the beginning."
Defeat was a bitter pill for Arsenal to swallow after three successive victories had helped to rekindle a sense of optimism after a mediocre start to the season.
Yet the way Wenger's side responded to adversity drew applause from the home crowd at the end and had it not been for an inspired display by United keeper David De Gea, Arsenal might have continued their winning run.
"I don't know if you've watched many top-level games but when you have 33 shots at goal in a game of that stature it means that our dominance was top class," Wenger said.
"But I'm angry and disappointed because we had nothing to show for it. I am proud of their commitment and attitude, I feel sorry for the players that gave so much."
Arsenal slipped to fifth spot with 28 points from 15 games, a point behind Liverpool and 12 behind leaders Manchester City who are in action on Sunday at home to West Ham.
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