Ferguson: Liverpool form no omen for derby
"Derby games are derby games and anyone can win it," Ferguson told reporters. "It has happened so many times and strange things can happen.
"I am not interested in their league form, I am more pleased with the kind of form we are in. We are consistent and consistent is important."
Liverpool's worst run of form for 22 years continued on Tuesday when they lost to Olympique Lyon at home in a Champions League group match.
Previous defeats to Fiorentina, Chelsea and Sunderland have turned the spotlight on manager Rafa Benitez like never before in his six-season tenure.
With Fernando Torres and Steven Gerrard unlikely to be fit for the United match, a loss this weekend could prove terminal for Benitez's ambitions on Merseyside.
Manchester City consider themselves United's biggest rivals because of the proximity of the two clubs but Ferguson said United v Liverpool would always be a superior contest.
"Manchester United and Liverpool games, as I have said many times, are massive games," Ferguson said. "That will never change and as far as I am concerned it remains the game."
United lead the Premier League by one point from Chelsea, while Liverpool are seven points behind in eighth place.
Liverpool won 2-1 at Anfield last season before shocking the eventual Premier League champions 4-1 at Old Trafford in a stunning performance.
However, Ferguson said those matches would have no bearing on Sunday's game.
"Different games are shaped differently by the circumstances of those games and you cannot look at last season as a barometer of our form or Liverpool's form," he said.