Sir Alex Ferguson is demanding another Manchester United win at Sheffield United on Saturday to ensure his side retain a three-point lead over Chelsea going into their mouth-watering showdown the following weekend.The Red Devils have record six straight Barclays Premiership wins since the disappointing draw at Reading in September, a run which has allowed them to sneak a lead on Chelsea, who have already twice stumbled unexpectedly this term. With a healthy goal difference advantage as well, Ferguson knows his team will retain top spot ahead of Chelsea's visit even if they lost at Bramall Lane and the Stamford Bridge outfit come through their London derby with West Ham unscathed. But the United manager knows just how much the pressure would be eased if they could beat the Blades to maintain a buffer on the back-to-back champions. 'The game with Chelsea will be a massive one and we want to be going into it with a three-point lead,' said Ferguson. 'Chelsea's excellent starts to the last two league campaigns are the main reason why they've won the title. 'They have left us all catching our breath, but thankfully we have enjoyed a good opening to the season this time round.' Having dropped points in just two of their opening 12 fixtures - their only defeat coming on home soil against Arsenal - United are enjoying one of the best starts to a league season in Ferguson's 20 years as manager. But the Scot is acutely aware the title race is a long way from over. Once the Chelsea game has gone, United will then embark on a testing run of eight games in five weeks, which includes trips to Manchester City, West Ham and Aston Villa. Even if they come through those tests, Ferguson accepts his team will probably stumble at some stage. And the Old Trafford chief believes it is how they react to such setbacks that will determine whether United land their ninth Premiership crown. 'The consistency factor comes in to play now,' he said. 'After the game with Chelsea you then go into the December programme - which is always congested, tense and exhausting for everyone. 'There has been a real increase in momentum from us and the performances on the field are justifying a lot of people's optimism at the club. 'But I don't want them to get too confident because there are a lot of potholes ahead and they will trip up somewhere. 'The important thing is how you recover. You have to have the consistency that champions need and the kind that we've had many times in the past.' As usual, Ferguson will hope his international stars return home without injury this week, although already there is a minor worry over Ryan Giggs, who picked up an ankle knock leading Wales to victory over Liechtenstein in Wrexham last night.