London - 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," Wenger said.
"It is another game where people look at us and see how we behave because even if Chelsea are not in the best position you look at their squad.
"It is a big game because of the quality of players on the pitch and it has a big importance to us because we play at Emirates Stadium and we know it will be important to win these types of games."
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.