Arsenal assistant manager Steve Bould admitted the Gunners look jaded following their 2-0 Champions League defeat by Schalke at Emirates Stadium.
It was the club's second successive defeat, arriving four days after their Barclays Premier League loss at Norwich, and their first at home in the group stage of Europe since 2003.
The result has placed Schalke in command of Group B and Bould, speaking in place of Arsene Wenger who was serving the final game of a three-match touchline ban, felt they lacked energy.
"We didn't play anything like we can, that was the big disappointment," he said.
"We haven't performed and we lacked confidence for whatever reason.
"It's a tough competition and Schalke are a good side who beat Dortmund at the weekend.
"They're doing really well and a 0-0 would have delighted us. We looked like we were going to get away with it for a long time.
"We looked jaded, I don't why that is. Since coming off the international break we haven't performed.
"We were very sharp against West Ham but since returning from the internationals we've been jaded."
Klaas Jan Huntelaar and Ibrahim Afellay capitalised on slack defending to score in the final 15 minutes.
Angry supporters left in their droves once Afellay had put the result beyond doubt and the few that remained booed at the final whistle
"We've lost at home and of course they're frustrated, we are as well," Bould said.
"We don't like losing football games, but we have to pick ourselves up and start again."
Arsenal were restricted to just one shot on goal in the entire match and had to wait until extra time for that with teenage substitute Serge Gnabry producing a late attempt.
But their failings in their own area were more damaging with both goals - just reward for Schalke's second-half dominance - exposing a fragile defence.
"The lack of chances isn't worrying, but it's not what we want or are accustomed to," Bould said.
"We normally create chances and now we're not, so we need to correct that."
Bould revealed that Theo Walcott would miss Saturday's Barclays Premier League clash with QPR due to his bruised lung.
However, Alex Oxlade-Chamberlain is back from a hip problem while Jack Wilshere should be available for selection.