When Arsenal were flailing three weeks ago they hit back by beating Manchester United and now, after another domestic setback, they have to find another big performance at leaders Chelsea to stay in the title race.
The Stamford Bridge clash (2130 IST) is one half of a heavyweight Sunday double bill as Manchester United also visit Manchester City (1900 IST).
Liverpool, on the same points as the leaders but with an inferior goal difference, are at home to West Ham United on Monday night.
Chelsea and Liverpool have 33 points with United on 25 but with a game in hand. After last week's 3-0 defeat by Manchester City, Arsenal have slipped to fifth on 23.
Defeat on Sunday would leave them 13 points adrift of Chelsea, and by Monday Liverpool too could be almost out of sight with United right behind them.
Manager Arsene Wenger has, for pretty much the first time in his 12 years at the club, started to attract grumbles.
His failure to add significantly to the squad in the close season has left fans frustrated and, starved of league success for the last four years, the undefeated championship season of 2003-04 is becoming a distant memory.
Wenger can point to a crop of promising youngsters highlighting their talents in the League Cup but it will take a while for most of them, if they make it at all, to become first-team regulars.
Two exceptions, however, seem to be 16-year-old midfielder Jack Wilshire, who had his first taste of European football in Tuesday's 1-0 win over Dynamo Kiev, and Welsh midfielder Aaron Ramsey, who is improving with every game.
The midweek victory propelled Arsenal safely into the Champions League knockout phase with a game to spare and brought some much-needed good news to the club.
"That was the first step, what the team needs is a bit of reassurance and it will give us that," Wenger said after Nicklas Bendtner's late strike.
Cesc Fabregas, installed as captain after William Gallas was stripped of the role for criticising his team mates, said: "We showed we are united. The attitude was spot on."
Emmanuel Adebayor, Samir Nasri and Bakary Sagna could return from injury against a Chelsea side who absorbed their home defeat by Liverpool last month to surge back to the top of the league.
Chelsea were made to wait, however, for a berth in the last 16 of the Champions League when they were held 1-1 away by Girondins Bordeaux on Wednesday.
Chelsea are without suspended Didier Drogba on Sunday but are buoyed by the hot form of Nicolas Anelka, whose opener at Bordeaux took his tally to nine goals in his last seven games.