Arsene Wenger admits it is difficult to imagine English football without Sir Alex Ferguson.

The Manchester United manager will retire at the end of the season after 26 years in charge at Old Trafford, a spell that has brought his club 25 major trophies.

Wenger and Ferguson have enjoyed a great rivalry since the Frenchman arrived in England in 1996 and Arsenal's manager has praised his old sparring partner.

"It's a great void to fill for Manchester United, because the charisma and personality disappears suddenly in a club which has been dominated by it for such a long time"

"I would just like to pay tribute to an unbelievable achievement and a fantastic career," Wenger told Arsenal Player. "Basically the achievement is immaculate, when you look at the whole structure and consistency of the achievement. It is, of course, something exceptional.

"It is difficult to imagine English football without him, but it's now a reality and a fact. Of course the next manager has to fill in and show he has the dimension to do that. It is a big task for the guy who comes in."

David Moyes will leave Everton this summer to succeed Ferguson at Man United and Wenger believes the Scot has a solid base to work from - but difficult shoes to fill.

"What you can say still is that Manchester United are commercially and financially one of the strongest two or three clubs in the world, and that is still a good basis to start when you come in because you know the players are there, the team is there, and the potential is there," he said.

"They have developed very well and they are in a very, very strong position to deal with the problem they face. But of course it's a great void to fill for Manchester United, because the charisma and personality disappears suddenly in a club which has been dominated by it for such a long time.

"It's not an easy task to replace a person like that."