Chelsea started life under new manager Luiz Felipe Scolari in the autumn of 2008 with an impressive record of just one defeat in 14 Premier League fixtures, while also earning eight points from five Champions League fixtures.
However, Chelsea's one setback in the league had seen Liverpool bring an end to their remarkable 86-match unbeaten record at Stamford Bridge in the Premier League.
As for Arsenal, three defeats in four games threatened to derail their title challenge before the halfway stage of the campaign, and manager Arsene Wenger was under pressure to improve on a record of just seven Premier League wins in 14 matches.
Scolari was forced to name an attack-minded midfield, with Michael Ballack, Frank Lampard and Deco featuring as the central three, while Emmanuel Adebayor and Robin van Persie provided the ammunition for the Gunners up front.
Arsenal began the game on the front foot, and former Blues defender William Gallas came near to converting a close-range effort after Petr Cech had done well to prevent a Samir Nasri shot finding the net.
© Getty Images
Cesc Fabregas also came close to netting the opener as Arsenal continued to dominate the first 30 minutes of the match, but Chelsea dealt the Gunners a sucker-punch 14 minutes before half time by taking the lead against the run of play.
Van Persie led Arsenal's response by forcing Cech into another stop, but after reaching the break ahead, Chelsea returned for the second half with a spring in their step, and they should have doubled their advantage through Lampard, but the England international failed to connect properly from 18 yards.
That missed opportunity came back to haunt Chelsea as Arsenal evened things up with a fortuitous equaliser shortly before the hour. Denilson played in Van Persie, who looked suspiciously offside, but the flag never went up to leave the Dutchman to drive the ball past an helpess Cech.
The home side were furious with the decision, but their pain worsened three minutes later when Van Persie struck again to hand the North London outfit the lead.
© Getty Images
Fabregas floated a free kick into the penalty area for Adebayor to rise above the Chelsea defence, and the Togolese striker's header found Van Persie to fire a superb effort past Cech.
Scolari introduced Florent Malouda and Miroslav Stoch, but as the minutes ticked by, Chelsea struggled to launch any kind of assault on Almunia's goal, with Arsenal looking the more likely to extend their lead.
Cech was forced to deny Denilson as the game entered added-on time, but the Gunners held on for a morale-boosting triumph as Chelsea slumped to their second home loss of the campaign.
The defeat acted as a catalyst for a number of indifferent displays from Chelsea, and a run of four victories in 10 league fixtures saw Scolari lose his job after a goalless draw with Hull City.
In stark contrast, Arsenal went on an incredible 21-match undefeated streak as they made sure of Champions League qualification, but ironically, their run came to an end after a 4-1 defeat to Chelsea at the Emirates Stadium.