Images from Saturday's action in the Premier League.
Chelsea's resurgence was brought to a shuddering halt by local rivals Brentford as Mauricio Pochettino's team suffered a demoralising 2-0 home defeat, but Arsenal's strong start continued with a 5-0 rout of Sheffield United on Saturday.
After beginning the season poorly it had appeared Chelsea might have turned a corner with back-to-back Premier League wins over Burnley and Fulham before an impressive 2-2 draw with Arsenal.
But their well-chronicled failure to convert chances returned as Brentford won at Stamford Bridge for the third successive time since gaining promotion to the top flight.
A thumping header by defender Ethan Pinnock gave Brentford the lead in the 58th minute and, with Chelsea having thrown everyone forward, Bryan Mbeumo rubbed salt in their wounds with a second goal on the counter-attack in stoppage time.
Chelsea's fourth defeat of the season left them in 11th with 12 points from 10 games -- hardly the sort of return the club anticipated when they spent a huge amount of money on new signings.
"The frustration is so massive," Pochettino said in an interview with talkSPORT radio, saying a strong first-half performance had given way to a lack of calm after the break.
"We need to be clinical and score more goals. This is what is missing... We need to keep believing."
Brentford's second successive win moved them above Chelsea with 13 points.
Manager Thomas Frank said he had spoken a few home truths at halftime after a poor first half by his side.
"I was disappointed with our performance and the first thing I said to the players (at half-time) was, believe, you're so much better than that," the Dane said.
Arsenal began the day five points behind leaders Tottenham Hotspur after their arch-rivals beat Crystal Palace 2-1 on Friday, but cut that gap to two points in rampant fashion.
Eddie Nketiah's first Premier League hat-trick was the biggest talking point of the day -- the newly-capped England striker scoring his first goals since August.
Nketiah, replacing the injured Gabriel Jesus, broke the deadlock in the 28th minute with a fine finish after a pass by Declan Rice and made it 2-0 shortly after halftime with an emphatic strike after United keeper Wes Foderingham failed to intercept Bukayo Saka's corner.
The best was saved until last, though, with Nketiah smashing an unstoppable shot into the top corner just before the hour before retrieving the ball and holding it aloft.
"For me he is top level. He's started nine out of our 10 Premier League games. That shows how much we trust him. A hat-trick for an academy player he needs to enjoy that. Hopefully, there's many more to come," manager Mikel Arteta said.
A Fabio Vieira penalty and Takehiro Tomiyasu's first Arsenal goal completed the demolition as Arsenal moved into second spot.
A hamstring injury to Wolves forward Pedro Neto cast a cloud over Wolverhampton's 2-2 home draw with Newcastle.
"We're all hopeful we don't miss him for very long," Wolves manager Gary O'Neil said of his talismanic winger. "Any team in this league would miss a player of Pedro's quality."
Callum Wilson netted a brace for Newcastle, who are unbeaten in six games, while Hwang Hee-Chan scored the equaliser for Wolves.
Sheffield United stayed rooted to the bottom with one point from 10 games and fellow promoted side Burnley are not doing much better, losing 2-1 to Bournemouth.
Burnley went ahead in the 11th minute when Charlie Taylor hammered home a fierce volley but Antoine Semenyo equalised before Philip Billing netted an extraordinary lob from 40 yards to earn Bournemouth their first win of the season.
Bournemouth moved out of the relegation zone with six points while Burnley are second bottom with four.
A busy Sunday programme features Manchester United taking on champions Manchester City at Old Trafford while Liverpool face Nottingham Forest.