The Manchester United manager, Sir Alex Ferguson, has warned Arsenal's unhappy fans to be careful what they wish for.

Although the Gunners eased some of the immediate pressure on Arsène Wenger by reaching the Champions League group stage this week, the north London club head to Old Trafford on Sunday having collected just one point from their opening two Premier League games.

That meagre return, the loss of Cesc Fábregas and Samir Nasri, Wenger's transfer policy which has left many supporters distinctly underwhelmed and six seasons without a trophy have led many to start thinking the previously unthinkable and wonder whether a change at the top is required.

But Ferguson wonders exactly who those hard-to-please fans have in mind as a potential replacement.

"I would like to know who is going to replace him," said the United manager. "The work he has done in the 15 years he has been at the club is the best in Arsenal's history. Yes, he has not won a trophy for six years but what does that mean? The quality of his side has not been reduced."

Rather, as Ferguson points out, the standard of opposition has improved, first through the vast riches lavished on Chelsea by Roman Abramovich, and now the even deeper pockets of Sheikh Mansour at Manchester City.

"Chelsea's involvement has created a lot of the problem in terms of trophies to win because they and ourselves have been dominating the Premier League," said Ferguson. "Now Manchester City have come on the scene. When Arsenal and ourselves were going head-to-head, it went on for about eight years. The competition is far greater now."

Not that Ferguson expects supporters of any club, including his own, to adopt a reasoned view of proceedings. As he is fond of saying, the world is different now compared to the one that existed before Wenger replaced Bruce Rioch at Highbury in the autumn of 1996.

"It is a bit unfair of course. But who understands fairness and unfairness today?" he said. "It is quite a cynical world. Supporters are far less easy to please than they were 20 years ago. It is disappointing.

"But [Arsenal] answered everybody back on Wednesday. They got a great result and the game on Sunday will be another stepping stone for them."

Ferguson certainly will not be taking Arsenal lightly, even though his own youthful side have started the season with a bang, firing three second-half goals past Tottenham on Monday after an opening weekend win at West Brom.

The question United's manager is faced with is whether to stick with the likes of Tom Cleverley now Darren Fletcher is available to beef up his midfield, or if he should leave out either Jonny Evans or Phil Jones in favour of Rio Ferdinand if the England veteran recovers from a hamstring strain.

Even more eyecatching is the battle between Danny Welbeck and Javier Hernandez for the right to partner Wayne Rooney in attack. It seems Ferguson is leaning towards his kids.

"I have a tremendous problem when it comes to picking a side but it is the kind of problem I want," he said. "They [the younger players] have only played a couple of games. We are very enthusiastic about their potential but the name of the game is what they achieve.

"Maybe some of their form will taper off. That is when the squad comes into play. At the moment they are doing very well. So I have to let it carry on."