Arsene Wenger accused Arsenal of falling well below the standards they have set for themselves after losing 3-2 at home to West Bromwich Albion.
A downbeat Wenger pulled no punches after seeing his side beaten for the first time in the Premier League this season.
The Baggies thoroughly deserved their success in the capital, spurning a chance to take the lead in the first half when Manuel Almunia saved Chris Brunt's penalty.
Peter Odemwingie broke the deadlock five minutes after the restart, converting a Jerome Thomas cutback, before Almunia spilled a Gonzalo Jara effort into the net to make it 2-0.
When Thomas shot home from Brunt's pass with 17 minutes to play it was game over, with Samir Nasri's late double not being enough to rescue a point for the shell-shocked Gunners.
"It was a poor performance, defensively and offensively," said Wenger.
"Not one player performed to their level. We had an off day and were not good enough to win the game.
"We were not capable of the right level of concentration. The concentration that gives you the sharpness was not there today.
"We were poor everywhere – at the back, up front and in the middle of the park. Anything was difficult for us today, to pass the ball, to win it back.
"Overall we got what we deserved, that is zero points. We didn't deserve more."