Arsenal snatched top spot in the Premier League with a dramatic 1-0 win at Brentford Saturday.
The Gunners took first place thanks to Kai Havertz's late goal in west London.
Havertz was a Champions League final hero for Chelsea in 2021, but he has endured a torrid time since crossing London to join Arsenal in the close-season.
The 24-year old midfielder finally gave a glimpse of why Mikel Arteta splashed out £65m ($80m) to sign him when he met Bukayo Saka's cross with a close-range header in the 89th minute.
Havertz's second goal for Arsenal was his first in his last 10 appearances, moving his team one point clear of second placed Manchester City.
At St James' Park, injury-hit Newcastle United crushed Chelsea 4-1 as Blues boss Mauricio Pochettino labelled his side "soft".
Sixth placed Newcastle were stretched so thin that Eddie Howe had to name three goalkeepers among his substitutes.
But they ignored their fitness issues to bounce back from successive defeats against Bournemouth and Borussia Dortmund.
Newcastle striker Alexander Isak fired home from Lewis Miley's pass to open the scoring in the 13th minute.
Chelsea's Raheem Sterling equalized with a superb free-kick 10 minutes later, but Jamaal Lascelles restored Newcastle's advantage with a header on the hour.
And less than 60 seconds later, Joelinton punished Thiago Silva after the Chelsea defender mis-controlled Cole Palmer's pass.
Chelsea right-back Reece James was sent off for a second booking in the 73rd minute and Newcastle rounded off their demolition 10 minutes later when Anthony Gordon slotted home.
It was the heaviest defeat of Pochettino's first season in charge and the second successive game that Chelsea conceded four goals.
"We were so soft in every single challenge. We didn't show that we were playing for something important. That's what makes me angry and disappointed," Pochettino said.
Fourth bottom Luton Town secured their first home league win this season as Crystal Palace were beaten 2-1 at Kenilworth Road.
West Ham United staged a late fightback to steal a 2-1 win that added to rock bottom Burnley's relegation fears.
Brighton and Hove Albion won for the first time in seven league games as Joao Pedro inspired a 3-2 victory at Nottingham Forest.
Marcus Tavernier scored twice as Bournemouth won 3-1 at third bottom Sheffield United.
RESULTS
Brentford 0 Arsenal 1 (Havertz 89)
Burnley 1 (Rodriguez 49-P) West Ham 2 (O'Shea 86-og, Soucek 90+1)
Luton 2 (Mengi 72, Brown 83) Palace 1 (Olise 74)
Newcastle 4 (Isak 13, Lascelles 60, Joelinton 61, Gordon 83) Chelsea 1 (Sterling 23)
Forest 2 (Elanga 3, Gibbs-White 76-P) Brighton 3 (Ferguson 26, Pedro 45, 58-P)
Sheffield Utd 1 (McBurnie 90+7) Bournemouth 3 (Tavernier 12, 51, Kluivert 45)
