Chelsea manager Jose Mourinho yesterday hit back at Alex Ferguson over his suggestion that Chelsea's title challenge will collapse in the north of England by declaring: "You're not so good in the South."

Ferguson claimed that Chelsea's title challenge could be de-railed when the Londoners travel to play more northern sides in the New Year.

The United manager, a past master at mind games, warned the Premiership leaders that they have only travelled further north than Birmingham in the league on two occasions so far - losing against Manchester City and winning at Middlesbrough.

Chelsea, who go into the Christmas period five points clear of Arsenal and nine ahead of United, face visits to the northern outposts of Blackburn, Everton, Bolton, Newcastle and, of course Old Trafford, in the second half of the season and Ferguson insisted: "Chelsea will find it difficult coming north to get points."

Both Arsenal manager Arsene Wenger and Ferguson also expect Chelsea to drop points over the Christmas and New Year period.

But Mourinho is relishing the challenge of his first English Christmas and New Year programme and added that Manchester United had hardly been a raging success down south.

Mourinho said: "Maybe they are correct. If we drop a lot of points in this period it is because they are correct. If we can remain top of the league after this period, it is because they are incorrect. We will have to wait and see.

"But for sure Manchester United lose points in the south. They lost three points at Stamford Bridge, they lost three points at Portsmouth and they lost two points at Fulham. So for sure, they have a problem in the south. We have to wait to see if we have a problem in the north - maybe it is true.

"Maybe I will face something that I don't know, that is unbelievable up north. I look forward to it because I am always learning. So if I go there and I learn something, it is great."

Of more immediate concern for Mourinho is the strength of his squad. He is without the services of defenders Robert Huth and Celestine Babayaro as well as midfielder Scott Parker for the St Stephen's Day clash with Aston Villa at home.

Centre-half Ricardo Carvalho, who missed the win over Norwich is rated as doubtful.

The loss of Parker, who is expected to be out until March with a broken foot, has not changed Mourinho mind about new signings and he re-iterated yet again moves for Tottenham striker Jermain Defoe or Real Betis winger Joaquin.