Sir Alex Ferguson is set to play Cristiano Ronaldo from the start at Stamford Bridge after admitting that Manchester United cannot afford to lose to Chelsea on Sunday.

The champions will be nine points behind Luiz Felipe Scolari's men if they are beaten in west London.

United have looked far from impressive this season and crashed to a 2-1 defeat against Liverpool at Anfield last Saturday.

The trip to Chelsea – unbeaten at home in the League since they lost to Arsenal in February 2004 – could not have come at a worse possible time for United.

Dimitar Berbatov, Paul Scholes and Owen Hargreaves are all struggling with injury and Michael Carrick (broken foot) and Nemanja Vidic (suspended) are defintely out.

The one glimmer for Ferguson came when Ronaldo returned for half-an-hour as a substitute against Villarreal in midweek, and the manager admitted that he will have no fears over starting the 23-year-old on Sunday.

He said: “The boy is a natural athlete and he has trained very well, so I would have no qualms about him playing against Chelsea. It is just a questionas to whether this is the right time, but I have no fears about him and he is bursting to play. He has been nibbling at my ear all week.

“Whether this is a crunch game or not, I wouldn't like to say, but it is still big game for us because, when you play the big ones, you want to come away with a good haul.

“We did well against the Big Four last season, but with what happened at Liverpool last week, we have lost one of those big games already and we can't afford another one. I'm not worried about our performances, though and once October comes, we'll be fine, I'm sure.”

Ferguson insisted his players are strong enough to claw their way back into the title race, despite Chelsea's impressive start.

He said: “This is not a test of character because the character of my team is well established. It is just another game for us to bounce back from a defeat.

“People aren't expecting us to win, which is unusual for Manchester United.”

In fact, Ferguson still sees United's match with Arsenal on 8 November as a bigger game as Chelsea cannot match the “history and quality” of their London rivals.

Speaking at the League Managers' Association's dinner for their Benevolent Trust and Community Fund at Wembley, Ferguson said: “If you look back over the last 12 or 13 years, who has it been? Arsenal v Manchester United.

“Of course we've got Chelsea at the moment, that's without question, but the history of Arsenal versus Manchester means that you're not just talking about winning a football match, you're talking about your own history against the other team's history.”