Manager praises "great fans" who made the trip to Old Trafford and accepts criticism, and says he will spend the money available to him if he finds the right players
The 61-year-old wrote to Arsenal fans in a newsletter, and partly blamed the defeat on the side being fatigued after their midweek Champions League qualifier against Udinese, before calling for his team to show "strength and desire" in their next game.
He also stated that it was clear that the team was "short in some areas" and that money was available to buy players.
"Our fans were great at Old Trafford on Sunday and I feel sorry for them. They do not want to see their team like that," he said.
"I can only apologise for the scoreline. Now we must respond by showing strength and desire in our next game. The players go away for two weeks and when they come back we'll have to prepare.
"We have played three games in the Premier League and two Champions League games. It is not a time to make a balance of the whole season but of course an 8-2 defeat is humiliating.
"You could see that we had not recovered physically from Wednesday night's game at Udinese and we were short in some areas, that is for sure.
"Manchester United have class and they punished us with some great finishing. We missed a penalty and we had a chance to get back to 3-2 but after that we opened ourselves up.
"I have been criticised and I have to accept that because I am in a public job. I try to make the right decisions for the club and I will continue to do that.
"If you look at the 15 years I have been at the club, I have brought in some good players. The transfer window closes on Wednesday and we have the money to sign more players.
"If we find someone who can strengthen our team then we will do it."