Arsenal capitalised on Manchester City's stumble to establish a commanding four-point advantage atop the Premier League table following their narrow victory against Crystal Palace on Sunday.
The decisive moment arrived through Eberechi Eze's spectacular scissor-kick against his previous employers, converting after Declan Rice's delivery deflected off Ismailla Sarr.
The £67.5 million summer signing demonstrated no sentiment towards his former side, hammering the ball past the Palace defence six minutes before half-time.
The Gunners' triumph gained additional significance as City suffered their first defeat since late August, falling to Aston Villa whilst Liverpool endured another setback at Brentford on Saturday.
Eberechi Eze returned to haunt his old club to make it a very happy weekend for Arsenal
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Matty Cash's powerful strike from the penalty area's edge after 19 minutes proved sufficient to hand Pep Guardiola's team their first reverse in nearly two months.
The defeat terminated Erling Haaland's extraordinary 12-match scoring sequence for both club and country, which had stretched back to 23 August.
The Norwegian forward believed he had salvaged a point in the 89th minute, sliding the ball home before colliding with the post, but officials ruled the effort out for offside after Phil Foden strayed beyond Villa's defensive line.
Villa's triumph marked their third consecutive home victory against City and celebrated Unai Emery's third anniversary at the helm in perfect fashion.
Liverpool's struggles persisted with a 3-2 reverse at Brentford on Saturday, marking their fourth consecutive league defeat and leaving them seven points adrift of Arsenal.
Matty Cash's sublime strike ended City's nine-match unbeaten run
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The champions' poor form has created an unexpected Premier League hierarchy, with Bournemouth occupying second position following their 2-0 home victory against Nottingham Forest.
Perhaps most remarkably, newly-promoted Sunderland sit third in the standings, one point behind Bournemouth and ahead of fourth-placed City.
The weekend's results have transformed the title race dynamics, with Arsenal's traditional rivals faltering whilst unfancied sides capitalise on their opportunities to climb the table.
Mikel Arteta enjoyed a fine weekend with City, Liverpool and Chelsea all losing
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Mikel Arteta's squad has now secured seven successive victories across all competitions, maintaining their formidable defensive record with just three goals conceded in 13 matches this campaign.
The north London side recorded their fifth consecutive clean sheet, with Palace failing to register a single attempt on target throughout the encounter.
City are now six points behind league leaders Arsenal
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However, concerns emerged when William Saliba departed at the interval with an injury, whilst Declan Rice limped off during the closing stages.
These fitness worries represent the sole blemish on an otherwise ideal weekend for Arsenal, who conclude October at the league's summit before Wednesday's Carabao Cup fixture against Brighton.