The 25-year-old Ivorian started alongside Thomas Vermaelen at the heart of the defence for the Gunners as they crashed to a surprise 2-1 defeat at home to lowly Wigan Athletic.
And Djourou believes that Arsenal must step up their game against Chelsea to help seal third place, and with it qualification for next season's Champions League group stage.
"They still want to have Champions League football next season as well so we know it is going to be a tough game," he told Arsenal's official website.
"Obviously they have a lot of fixtures, the two Barcelona games are [either side of Saturday's derby] but we don't really concentrate on that. We have to be focused on our game and be focused on what we do best.
"We need to play football the way we did against Manchester City and Wolves, that is the sort of situation we have to get back into. We have to show that again. Unfortunately it wasn't the case against Wigan but we have to be sure it is there on Saturday."
Arsenal missed the chance to extend their hold on third spot to eight points against Wigan, but the Swiss international still feels the North London side are in pole position.
"Of course we are and we would rather be in that situation," he said. "It was a disappointing result, we know that, and now we have to dig in and just go forward because Saturday is around the corner and we have to make sure we are ready for that."
