Arsene Wenger said he was humiliated by the crushing 8-2 defeat at Premier League rivals Manchester United.
Wayne Rooney scored the sixth hat-trick of his Old Trafford career as United went back to the top of the table and left Wenger facing a growing crisis.
"Of course you feel humiliated when you concede eight goals," said the Arsenal boss. "It was a terrible day."
Sir Alex Ferguson said: "He has been a big adversary and will continue to be when he gets his big players back."
Wenger insists it is too early to judge whether his summer transfer policy has been flawed following the departures of Cesc Fabregas and Samir Nasri and the lack of midfield replacements.
But he is now battling to sign reinforcements before the transfer window closes at 2300 BST on Wednesday.
Wenger, who insists he will not quit, expects to complete the signing of Monaco's South Korean striker Park Chu-Young before then.
He also wants to sign a central defender and a midfielder, and Arsenal are likely to renew their interest in Bolton centre-half Gary Cahill, having already had one bid turned down.
Wenger, who became Arsenal manager in October 1996, added: "We have to find the right players and if we do we will sign them. We have the money and if we find players to strengthen the team we will do it. If we don't do it, it is because we haven't found them.
"I try to make the right decisions and the two players we sold [Fabregas and Nasri], I brought them to the club. In 15 years I have brought some good players.
"You know me, so you should give me some more time to see if I have got it completely wrong."
After Arsenal's worst defeat since 1896, when they lost 8-0 away at Loughborough Town in Division 2, Wenger added: "I do feel it was under special circumstances.
"We had a lot of players out and we have played only five games. We collapsed physically towards the end but we had eight players out."
United boss Ferguson offered words of comfort, saying: "We live in a cynical world these days and the media are so cut-throat.
"He has introduced a philosophy of football and a way of playing and has brought in entertaining players and has sold fantastically well. I respect that.""It is hard to understand at times, but the job he has done for 15 years now is phenomenal.
Arsenal captain Robin van Persie, who had a penalty saved when the Gunners were 1-0 down, concedes his team must improve before their next league game at home to Swansea on 10 September.
"We need to come back," said the striker. "We have Swansea in two weeks, which is a good opponent and I look forward to that.
"This was the strongest team we had today. We gave our maximum but it was clearly not good enough.
"I don't think we can hide behind injuries or suspensions. It is no excuse. They had injuries too, this is football."
Former Arsenal defender Lee Dixon said the Gunners were already out of contention for the title but insisted Wenger was still the man for the job.
"You can rule Arsenal out of the championship based on this performance and size of this squad," said Dixon.
"But he's the right man for the job. I still think he has a lot to offer Arsenal and it will be a matter of time before he does strengthen the squad."
Dixon blamed the defeat on a lack of strength and depth and the absence of a clear game plan.
"Arsenal had an inexperienced team and bench and that showed from the start not just in the way they played but in the manner in which they got beat," said the former right-back.
"They were going forward when they shouldn't have been going forward, dropping off when they shouldn't have been dropping off and leaving a huge amount of space behind.
"When you go to Old Trafford you need a game plan, whether you put your first team out or you have got a young team. On Sunday, they had no plan whatsoever."