Sergio Aguero wants to put pressure on Premier League leaders Chelsea by claiming victory in the Manchester derby on Sunday. City go into the derby at Old Trafford in fourth place, one point behind their neighbours after a 2-1 defeat at Crystal Palace on Monday. Manuel Pellegrini's team are nine points behind Chelsea, who have a match in hand against bottom side Leicester, but Aguero knows better than most that City are not averse to an 11th-hour comeback. Sergio Aguero insists Manchester City can retain the Premier League despite defeat by Crystal Palace . The Argentina international has struggled for form and fitness as City have slipped this season . The Argentinian scored a 94th minute winner to wrest the title from United's grasp in 2012 and he is not giving up on the top prize again just yet. 'Of course we can still win it,' the City striker told Sky Sports News. 'In football, anything can happen - as soon as you think something is certain, then everything changes, we have seen it so many times before and we'll see it again. 'We only focus on ourselves, try to win every game we play and keep pressure on Chelsea.' City have beaten United in the last four Manchester derbies: . 8 April 2013         United 1-2 City . 22 Sept 2013       City 4-1 United . 25 March 2014    United 0-3 City . 2 Nov 2014          City 1-0 United . Pellegrini's team were level with Chelsea on New Year's Day, but the Blues have pulled away recently after City lost three of their last five league games. United, in contrast, have won their last five matches, and Aguero is wary of the threat Louis van Gaal's team will pose at Old Trafford. He added: 'They are a team with a lot of great individual players, who can form an incredible unit when they work well together. But this season that has not always been the case. 'Some matches they don't seem to play at the maximum, with the attacking qualities that they have in the team. But then in other games, they have really shown that those qualities, so they are a bit unpredictable. We know we will have to be at our very best to beat them - there's no doubt about that.' The champions face Manchester United on Sunday, having won the last four derbies . Aguero has scored six times against United, including this one at the Etihad in September 2013 . Van Gaal came in for criticism at the start of the campaign after winning just three of his opening 11 matches in all competitions. Radamel Falcao was one of many new signings to struggle under the Dutchman. Seven months after signing the Colombian on a deadline-day loan deal from Monaco, he has scored just four goals for the club. Aguero remains a fan of the former Porto and Atletico Madrid forward, though. Aguero said: 'They have a number of very talented strikers. The one who in his career has been the most predatory is Falcao. 'He isn't having an easy time this season, but I really admire his commitment and his class and qualities are permanent. 'He is probably one of the most naturally-gifted strikers in football at the moment.' Aguero came face-to-face with 'one of the world's most gifted strikers' Radamel Falcao at a Puma event . Falcao has struggled to cement a starting place since arriving at Old Trafford on an expensive loan deal . Aguero has also struggled in front of goal recently, failing to find the net in the last five league games. However, he has scored six times against United and is aiming to add to that tally this weekend. 'I always love to score, but of course it is even more special to score in the big games,' he said. 'If you score against United at Old Trafford it almost give you shivers, because you can feel the tense atmosphere with most of the stadium being really quiet, but the away end going crazy. 'At home at it is different, when the City supporters are really loud in these games, it sometimes gives me goose bumps when they sing my name.'
Manchester City can still  mount a title challenge, insists Sergio Aguero .
Premier League champions face Manchester United in Sunday's derby .
Argentina ace has praised Old Trafford misfit Radamel Falcao .