Manchester United boss Sir Alex Ferguson has warned today's opponents Arsenal that they're due a dip in form sometime this season.

"I thought that Arsenal would make a strong challenge throughout the season and at this moment, that has proved correct," said Ferguson.

"But it's a long season and other clubs will have a say yet. I know from my own experience that there are rough days ahead.

"I said in pre-season that there was no way that Arsenal would want to be 20 points behind us again. I expected them to be stronger."