Arsene Wenger has praised Sir Alex Ferguson, after the Manchester United boss announced his retirement from professional football. The 71-year-old Scot will step down as Old Trafford manager in the summer, to be replaced by present Everton manager David Moyes. Wenger and Ferguson are two of the longest-serving managers in English football, and their rivalry over the years has been intense.

Arsene Wenger (L) and Sir Alex Ferguson

"I would just like to pay tribute to an unbelievable achievement and a fantastic career. 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," he told the Arsenal website.

Ferguson has won an incredible 38 trophies in his 26 years at United; the haul includes 13 Premier League titles, five FA Cups and two Champions League crowns. Wenger believes his old sparring partner's departure will leave a massive void at Old Trafford, something that Moyes will be hard-pressed to fill.

However, the 63-year-old Wenger also said replacing Ferguson would not be as hard as it has been made out, with the outgoing manager having provided a solid base for the present and the future.

"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," Wenger explained

"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," he concluded.

Ferguson will lead United against Swansea City on Sunday, which will mark his final home game in charge of the club. His final game will be at the Hawthorns next weekend, when he faces West Brom.