Tottenham boss Harry Redknapp said uncharacteristic bad defending was behind his side's 5-2 north London derby capitulation against Arsenal.
"We went 2-0 up but even then I could not say I felt over-comfortable," he said. "They were playing through us, outnumbering us and we had problems.
"At 2-2, we changed it and tried to thicken up in midfield but didn't.
"We didn't defend well all over the park and it was a big problem. We let people run and that's not like us."
Redknapp added: "We have been in great form, we are difficult to beat and are not a team that concedes goals like we did today."
Spurs led thanks to Louis Saha's early deflected strike and Emmanuel Adebayor's penalty.
But, despite their defensive frailties, the Gunners were still creating chances and two goals in two minutes by Bacary Sagna and Robin van Persie gave them the belief for a stylish second-half display which saw victory sealed with a Tomas Rosicky effort and two Theo Walcott strikes.
"I just wanted to get to half-time at 2-0 and I thought we would be okay," Redknapp added. "Suddenly I found us all square and we could have gone behind at half-time.
"We have to keep going. We've been great all year. We had a bad day and are all disappointed but we credit to Arsenal, they played ever so well. They are a dangerous team with real quality. They have a front man who is probably the best in the Premier League at the moment [Van Persie].
"They looked stronger today. I knew it would be tough game but when you are two up you cannot ask for a better position to be in."
Redknapp said the blip, which sees their lead over their bitter rivals closed to seven points, would not affect their belief or quest to finish as London's top club.
He said: "We want that third spot - that's what we are after. We have to make Champions League football. It won't be easy. Arsenal and Chelsea are strong sides.
"We have to pick ourselves up and get ready for the next game. We have a real tough run; Manchester United next week and Everton away and Chelsea away. It couldn't be any tougher."
Spurs will also have to face the reigning champions at White Hart Lane without influential midfielder Scott Parker, who was sent off in the closing stages of Sunday's defeat for a second yellow card.
"That's a big blow because he has been fantastic. That is a shame," said Redknapp, who also hinted that defender Ledley King may be a doubt.
"Ledley was struggling a bit with his hamstring and knees," he added. "I took a chance with him. He hasn't trained as normal. When he plays we normally win, but he found it a little bit harder today."