Alex Ferguson: Everyone will appeal now Vincent Kompany's red has been rescinded

United manager says ruling on City defender will 'open the door' to numerous challenges

Sir Alex Ferguson, the Manchester United manager, believes that the Football Association's decision to rescind the red card issued to Manchester City's Vincent Kompany at Arsenal last weekend is a flawed one that could open the floodgates to more appeals.

The potential for clubs to successfully challenge sendings off – a practice which was once virtually unknown – changed this summer when, after consultation with the clubs, the FA decided that for an appeal to be won, the error demonstrated must be "obvious" rather than "serious and obvious". But Ferguson feels that the high-profile nature of the Kompany decision will have an effect. "Anything I say about the situation will be regarded about bias so I'm not going to bother with it. It does open the door of course but that's their [the FA's] problem," he said. "I think that [appeals from everyone] are bound to happen now. But they will probably turn them all down now! I'm not going to go into it [any further]. Anything I say will be regarded as bias towards our immediate opponents or friendly neighbours."

City's manager Roberto Mancini has told Kompany to alter the way he tackles after his third red card in two seasons – two of them for challenges – was overturned. Kompany has been indignant about the legitimacy of his tackling, which briefly became a source of controversy when Ferguson said after the player's dismissal for a challenge on Luis Nani in last season's FA Cup third round that he was a serial offender. Privately, that comment infuriated Mancini.

Some Kompany tackles can lack control, as his feet leave the ground, even though they are made without malice. Mancini, who has Sergio Aguero and Jack Rodwell back in his squad for today's home match with Fulham, said the Belgian must "pay more attention" to his tackling. "Sometimes when a defender is under pressure he can do bad tackles but I think he needs to pay more attention. We can have a problem if we have another situation like this. I don't think he will change his style but in certain situations it could be better if you don't go in." Mancini insisted that strikers would not be able to take advantage of any indecision which the latest controversy may have created in the mind of Kompany.

Ferguson also offered a perspective on Liverpool manager Brendan Rodgers' public censure of Luis Suarez for admitting to diving in last October's goalless draw with Stoke City, observing that it was for clubs – rather than the FA – to drive out the scourge of simulation. "This was raised at the League Managers' Association meeting during the week," Ferguson said. "I think the FA have a problem because can they prove that a lad has positively tried to dive? They have no sanctions on diving. So it goes to the club [to resolve.] "You have to [speak to players firmly about it]. I've done it with Cristiano [Ronaldo]. He was only a young boy, 17, when he came in and it took him maybe a couple of years to understand that. But after that he was fine."

Ferguson offered his first public praise of Andre Villas-Boas, whom he meets when United travel to Tottenham tomorrow. "After his short spell at Chelsea it would have been quite easy to say, 'I'll just stay in Portugal, I think it is a bit mad over there'," he said. "But he took up the challenge."

United are without Jonny Evans, still carrying a hamstring injury, while Danny Welbeck has a sprained wrist ligament which requires him to wear a cast when not playing,

Meanwhile, City are reluctant to allow their 20-year-old striker John Guidetti out on loan this month because he is still in the early stages of recuperation after a nine-month lay off with a knee injury and has played only one Under-21 game since his return from Feyenoord, where he scored 20 goals in just 23 appearances.

The loan window extends into next month, which may create an opportunity. He has been in the sights of Swansea City, who may lack a striker if Danny Graham, unsettled at the Liberty Stadium, goes to Norwich City or Sunderland, who have come in with offers.