London, January 22 Arsene Wenger has warned Arsenal not to underestimate troubled Chelsea as the Premier League leaders bid to end their long barren run against their London rivals. The Gunners' 1-0 win over Chelsea in the Community Shield in August was Wenger's first success against his arch rival Jose Mourinho in 14 attempts. But that victory in the Wembley sunshine proved a false dawn for Arsenal in their attempt to end Chelsea's stranglehold over their derby showdowns. Wenger's men were beaten 2-0 at Stamford Bridge in September in one of the few highlights of a miserable campaign for Chelsea, who have since parted company with Mourinho and are now under the interim stewardship of Guus Hiddink heading into Sunday's clash at the Emirates Stadium. That loss meant Arsenal have failed to win any of their last eight league meetings with Chelsea dating back to their previous success in October 2011 and, even more remarkably, they have been unable to muster a single goal in the last five of those matches. Even in the plush surroundings of their own Emirates Stadium, Arsenal have found it impossible to banish the Blues, with no victories in their last five meetings in all competitions since their previous home win against Chelsea in December 2010. So, although Arsenal sit top of the table while spluttering champions Chelsea are languishing four points above the relegation zone in 14th place, Wenger has suffered enough against the west Londoners to know not to take victory for granted. 'They are not in this title race but I know the quality of their team. This season there have been exceptional circumstances for them and they will be back. I consider them direct rivals,' he said. By the time Arsenal kick off on Sunday they could have been replaced at the top on Saturday by second placed Leicester, who host Stoke, or third placed Manchester City, who travel to West Ham. Leicester are behind Arsenal only on goal difference but have struggled of late, winning only one of their previous seven matches in all competitions. But Foxes boss Claudio Ranieri insists he isn't concerned about the apparent loss of form of England striker Jamie Vardy, without a goal in six games, and Algeria winger Riyad Mahrez as his team's incredible season reaches a pivotal point. Manuel Pellegrini expects another difficult test of Manchester City's ability to win a 'different' title race when they travel to Upton Park. West Ham were unbeaten in eight league games before losing at Newcastle last week and are sixth in the table. Pellegrini's team brushed aside a Crystal Palace side enjoying one of their best top-flight seasons last weekend with a comfortable 4-0 home win. Fourth placed Tottenham face out-of-form Crystal Palace at Selhurst Park. Manchester United, buoyed by a 1-0 win at bitter rivals Liverpool that eased the pressure on boss Louis van Gaal, host Southampton as they look to close the gap on the top four and maintain their hopes of a title race.