Manchester United scored two late goals on Sunday to deepen the pain for beleaguered Manchester City boss Pep Guardiola as Chelsea moved just two points behind Premier League leaders Liverpool.
Elsewhere on a day of high drama in the English top flight, Wolves manager Gary O'Neil and Southampton boss Russell Martin were both sacked, paying the price for their teams' struggles.
In the marquee game of the day at the Etihad, City defender Josko Gvardiol opened the scoring but Bruno Fernandes levelled from the penalty spot in the 88th minute and Amad Diallo struck two minutes later to seal a 2-1 win.
Defending champions City – who have dominated English football over the past decade – now have just one win in 11 games in all competitions and Guardiola is desperately searching for answers.
"I don't have a defence, I'm the boss, I'm the manager. I have to find a solution and I don't find a solution," said the Catalan after the low-quality encounter.
"This is a big club, when you lose eight out of 11, something wrong is happening. What can I say? The schedule is tough, the injured players? No.
"I'm the boss, I'm the manager and I'm not good enough. It's as simple as that."
Guardiola's men trail leaders Liverpool, who have a game in hand, by nine points and sit outside the Champions League places, in fifth spot.
Injury-ravaged City were far from their best at the Etihad but appeared to be on course for a vital win as the clock ticked down against their neighbours before they self-imploded.
Matheus Nunes' sloppy back pass was cut out by Diallo and the Portuguese midfielder then chopped down the United winger in his attempt to make amends.
Fernandes coolly converted from the penalty spot to equalise.
Diallo then raced onto a simple long ball over the top of City's flat-footed defence, finishing neatly to complete a remarkable turnaround.
𝐌𝐀𝐍𝐂𝐇𝐄𝐒𝐓𝐄𝐑 𝐈𝐒 𝐑𝐄𝐃 🔴
— SuperSport Football ⚽️ (@SSFootball) December 15, 2024
Ruben Amorim tastes victory in his first Manchester derby 😤🔥#MCIMUN | #SSPremierLeague pic.twitter.com/jSuEV2Nt2f
The win is a huge relief for new United boss Ruben Amorim, who had won just one of his first four Premier League matches.
"I think for the fans it has a deep meaning, especially in this context, in this moment," the former Sporting Lisbon boss said after his first experience of a Manchester derby.
"We had a difficult moment one week ago against Nottingham (Forest) at home with a storm. It was a really tough moment after the game. Today, we are more happy, but it's three points that we have to continue."
United finished the day 13th in the Premier League table – where they started – after Tottenham hammered bottom club Southampton 5-0.
CHELSEA CHARGE
Enzo Maresca's high-flying Chelsea beat Brentford 2-1 at Stamford Bridge to close to within two points of long-time leaders Liverpool, who have 36 points.
The home team dominated the first half and got the reward they deserved shortly before the break when Marc Cucurella nodded home Noni Madueke's cross.
Nicolas Jackson doubled Chelsea's lead in the 80th minute and they held out for the win despite a late strike from prolific Brentford forward Bryan Mbeumo.
Nicolas Jackson makes up for his error 🤩
— SuperSport Football ⚽️ (@SSFootball) December 15, 2024
Chelsea are on their way to yet another league win ➡️
📺 Stream #CHEBRE on DStv: https://t.co/B0jLrQW5cc pic.twitter.com/3Gfjn7J7fK
It is a fifth straight win for Chelsea, who look increasingly like being Liverpool's main challengers this season, with Arsenal and City faltering.
But Maresca is still being coy over his side's title chances.
"It's not about how many games we win," he said. "It's about being realistic. There are things we have to do better. That's why I said for me we are not ready."
Tottenham's romp on the south coast was the latest chapter in a topsy-turvy season for Ange Postecoglou's men, who have now won seven and lost seven of their 16 top-flight matches.
James Maddison opened the scoring in 36 seconds and further goals followed for Son Heung-min, Dejan Kulusevski and Pape Sarr in a staggering 25-minute spell.
England midfielder Maddison grabbed a second goal deep into first-half stoppage time to make it 5-0 but there were no additions in the second half.
Sonny breaks records 🐐
— Tottenham Hotspur (@SpursOfficial) December 15, 2024
More Madders magic 🪄
Deki delight 🌟
Highlights: Southampton 0-5 Spurs 🍿 pic.twitter.com/gBLwmWrEw4
Shortly after the match Southampton issued a statement saying they had made the "difficult decision to part ways" with Martin with the club rooted to the bottom of the Premier League, nine points from safety.
Wolves, also in the relegation zone, fired O'Neil after a fourth straight defeat.
In the early kick-off, Ismaila Sarr scored twice as Crystal Palace moved four points clear of the relegation zone following a 3-1 victory at Brighton.