Sir Alex Ferguson said Manchester United will have to beware an Arsenal backlash when they meet in the English Premier League on Sunday.

The champions have started the season in style with successive wins, while their rivals have picked up just one point. United could have an eight-point advantage after the Old Trafford encounter, but Ferguson will take nothing for granted.

He is aware Arsenal and manager Arsene Wenger are hurting after their disappointing start and the sales of the inspirational Cesc Fabregas and Samir Nasri.

But a 2-1 win at Udinese took the Gunners into the Champions League group stage and lifted spirits as Ferguson fully recognises.

"They answered everybody back on Wednesday. His (Wenger) team played well. They got a great result. A lot of people thought they would go out. I didn't," he said.

"I thought they would win it. The game on Sunday will be another stepping stone for them. They will try to make sure they get a result, but we are in good form and are looking forward to it.”

"A Manchester United-Arsenal game is always contentious and significant in terms of the rest of the season. It is one you always look forward to."

While he will relish another test against his old foe, Ferguson has backed Wenger to come through a difficult period in his 15-year tenure as manager and cannot fathom the criticism directed at the Frenchman.

"It is quite a cynical world," he added. "Supporters are far less easy to please than they were 20 years ago. It is disappointing.

"I don't know the full story about Arsenal's finances. Some clubs have a financial restriction - that may be the reason. He has always sold very well. He still has great quality in his teams."

Fans unsure about ‘inconsistent’ Arsenal

Arsenal's lack of depth in their squad is one of the issues of concern for their supporters and not something United need worry about.

The return to fitness of Rio Ferdinand, Antonio Valencia, Javier Hernandez and Darren Fletcher - after a mystery virus - provides Ferguson with even more options and he added: "We are in a very healthy shape at the moment with the squad numbers.

"Darren Fletcher played a game (on Thursday), which is great news. The boy is back now. He has had a terrible time but now he is looking terrific and will be in the squad for Sunday.

"Rio is back training, Valencia is training well. Javier Hernandez came back on Monday, which gives me a tremendous problem when it comes to picking a side. But it is the kind of problem we want."

Youngsters shine for Red Devils

The impressive form of his young players has added to his selection problems and Ferguson feels they have earned their places - meaning more established players might have to be prepared for a spell on the sidelines.

Striker Danny Welbeck scored in the 3-0 win against Tottenham Hotspur last Monday, defender Phil Jones ensured a clean sheet while midfielder Tom Cleverley provided an assist for Welbeck's goal.

Wenger confident of Gunners’ form

Wenger, meanwhile, is convinced his players' success in qualifying for the Champions League group stages was a timely reminder that the Gunners remain one of Europe's elite.

"It is now 14 consecutive years that we have qualified for the group stages," the Frenchman said.

"And it's not as easy as it looks because only three teams have ever achieved that - Real Madrid, Manchester United and Arsenal."

The Gunners have yet to record a Premier League victory, having drawn 0-0 at Newcastle and lost 2-0 at home to Liverpool last week, with both games seeing one of his players sent off.

Wenger was sure the indisciplined days were behind them however. "I am confident we will be solid on Sunday and have a good performance," he said.

"We were under a lot of pressure and you could feel the tension in our side before the Udinese game. In the first leg I could feel the squad was a bit insecure and that was in our mind when we played Liverpool. That is out of the way now and I am confident you will see a much more convincing team in Manchester."

Defender Thomas Vermaelen faces a fitness test but Laurent Koscielny is able to return and Tomas Rosicky and Johan Djourou are also expected to shrug off fitness concerns.

Wenger will be without injured midfielder Jack Wilshere and suspended trio Gervinho, Alex Song and Emmanuel Frimpong.