Sergio Aguero has urged his Manchester City team-mates to "finish the job" and win the Premier League after their cross-city rivals for the title messed up at home to Blackburn yesterday.
United had been widely expected to be top of the table this morning but the shock 3-2 defeat means City can re-establish a three-point lead to kickstart the New Year at Sunderland this afternoon.
City established themselves as title favourites after losing just one of their opening 18 matches and Aguero wants an equally strong second half of the season. The Argentina striker feels the quality of the City squad has enabled him to settle quickly since his club record £38m move from Atletico Madrid last summer.
"I couldn't have wished for a better start to this new era in my personal and professional life, and everything I set for myself is being fulfilled," said the 23-year-old. "Fortunately, the adaptation was faster than I thought.
"It helped a lot to arrive at a club with a very serious project and a team with a solid base of great players and good people.
"We made a great start to the season and now we have to finish the job. We hope we can keep this pace. We want to win the league and we will give everything to succeed."
City were actually frustrated in their last outing as they were held to a goalless draw at West Brom on St Stephen's Day. They now face a test of their trophy credentials as they begin a tough January programme today.
The game is quickly followed by a home clash against Liverpool on Tuesday. City then face United in a mouth-watering FA Cup third-round tie and have two more clashes with Liverpool in the Carling Cup semi-finals as well as league games against Wigan and Tottenham.
Manager Roberto Mancini was not overly concerned by his team's failure to score for the first time this season at The Hawthorns but has warned against complacency.
"I think there will be some moments when we don't score goals or some when United score five goals, like in the last two or three weeks," he said. "But this is normal. We have 20 games and I think we will score in a lot of games in this championship. But if we want to win this title we should focus on every game. Thinking the game is easy is impossible. Every game is very difficult.
"When we play the likes of West Bromwich, like Sunderland, they will be tough games and we should concentrate 100 per cent. We want to win this title and will do everything to win this title. We must focus on the next 20 games and think positive, (especially) in difficult moments."
City were expected to beat West Brom comfortably but the Baggies were well organised in defence. By getting numbers back, manager Roy Hodgson found a tactic to frustrate City, who lacked their usual bite, and Mancini expects more of the same at the Stadium of Light.
"From now until the end we will find many games like the one against West Brom," said Mancini. "It will probably be the same against Sunderland. Sometimes if you don't pay attention you can risk losing.
"Against West Brom in the second half we conceded counter-attacks for some reason. It is important we score quickly in this game and take control."
Mancini is likely to make a number of changes and test the depth of his star-studded squad in the coming three days.
The Italian has regularly rotated strikers, wide midfielders and full-backs but even the likes of Yaya Toure and David Silva may be given time out. "David probably he needs a rest some time but he is very important for us. It is impossible for David, Yaya to play well always. It is impossible for any player. Sometimes they need to rest."
City have no injury concerns with full-backs Micah Richards and Aleksandar Kolarov back in contention.
Mancini, meanwhile, insists he is in no hurry to discuss a new contract with the club hierarchy. The 47-year-old has less than 18 months on his present deal but said: "I am happy, there are no talks. I don't have this problem. I need to focus on the team, on the championship."
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