Manchester City supporters ended a bad week by finding old enemy Manchester United closing to within two points of them at the top of the Premier League after a 3-2 victory at Southampton on Sunday.
A week ago City were five points clear of their neighbours, having not even conceded a goal in five matches, and the bookmakers were slashing their title odds.
Then after a hugely disappointing home defeat by Juventus in the Champions League, they were shocked by West Ham United's 2-1 victory at the Etihad that ended a 100 percent league record.
United rubbed salt into east Manchester wounds when they resisted Southampton's late rally thanks to some fine saves from goalkeeper David de Gea, who had seemed certain to leave in the recent transfer window.
Instead a deal with Real Madrid broke down on the last day of the window, when United also brought in Anthony Martial from AS Monaco as the world's most expensive teenage signing at 36.3 million pounds ($56.39 million).
Having scored as a substitute on his Premier League debut against Liverpool, he added two more goals at Southampton, both expertly taken.
Graziano Pelle put Southampton ahead in the 13th minute. Martial equalised 10 minutes before half-time with United's first shot on target, although Juan Mata should have been given offside, and the 19 year-old Frenchman put United in front following a dreadful back pass by Southampton's Japanese defender Maya Yoshida.
Mata added United's third midway through the second half before De Gea denied Jose Fonte and Pelle gave his team late hope by heading in Sadio Mane's cross.
"I have to make a lot of compliments to my players," United's manager Louis van Gaal told reporters.
"Anthony Martial is already special because we paid a lot of money for him. A lot of people are thinking he is a great star but he is a boy of 19."
Defeat put Southampton fifth from bottom with one win from six games and left manager Ronald Koeman rueing Yoshida's error.
"We lost by ourselves," he told Sky Sports. "The first 30 minutes we played perfect."
Liverpool's hopes of joining the title chase look forlorn after promoted Norwich City held them 1-1 at Anfield.
Despite having few chances in a dull first half, the home side went ahead with a goal by Danny Ings, only three minutes after he appeared as a half-time substitute for Christian Benteke.
But Norwich's central defender Russell Martin scored his third goal of the season to equalise after a mistake by goalkeeper Simon Mignolet at a corner.
Liverpool had started the game in the bottom six and a single point lifted them only two places to 13th, seven points behind the leaders.
"It was important that we got some flow in our game and our intensity in the second half was much better," manager Brendan Rodgers told the BBC.
"In terms of numbers it's not so good but for me it's all about the performance."
In the early match, Son Heung-min scored on his home Premier League debut for Tottenham Hotspur, who beat Crystal Palace 1-0 to continue their climb up the table to ninth place.
Spurs manager Mauricio Pochettino was delighted with Son,
who joined the London club from Bayer Leverkusen for 22 million pounds ($34.18 million) last month.
"His performance was fantastic and the energy he showed was amazing," the Argentine told reporters.