Sergio Aguero admits that Manchester City are worried about missing out on securing a place in next season's Champions League.
The Argentina striker concedes that it will be difficult to win the Premier League this season with City now 12 points behind leaders Leicester City with just nine games remaining.
And Manuel Pellegrini's side are in danger of losing their top-four place. West Ham United are just two points behind while neighbours United are four points adrift with the two clubs meeting at the Etihad on Sunday.
Aguero says it is crucial they beat their rivals in the derby, although the Blues will go into the game without skipper Vincent Kompany, after he suffered another calf strain in the midweek victory over Dynamo Kiev.
He told reporters: "We will be thinking about United -- we have to win, even more so because the title is slipping further and further away and we have to make sure we take fourth place.
"We want the title, but we have to take into account that United are right behind us and it will be a tough game, we will have to play intensely."
City have won just two of their last seven Premier League, and drew 0-0 at Old Trafford in November. However, they will go into the game as favourites with United in danger of missing out on the Champions League for the second time in three years.
It's a complete turnaround to when Aguero first joined the club from Atletico Madrid for £38 million in 2011, when United had just won their fourth title in five years while City were about to embark on their first-ever Champions League campaign.
The 27-year-old added: "I think that over the last five years City have always competed hard in the derby. But as you say at one point United were huge and City have invested a lot of money to bring in quality players and that has levelled the playing field.
"I don't know what is happening at United, I focus on City and Sunday. We are thinking about winning and nothing else."