Manchester City thrashed Manchester United 4-1 in an extraordinary derby match as Arsenal went top of the Premier League on Sunday.
In what was a first Manchester derby for both City manager Manuel Pellegrini and United counterpart David Moyes, Sergio Aguero scored twice at Eastlands with Yaya Toure and Samir Nasri also on target for the hosts.
The first match between the two clubs since Alex Ferguson retired as manager of English champions United at the end of last season saw Aguero open the scoring in the 16th minute when he flicked in Aleksandar Kolarov's cross despite the ball being behind him.
Toure made it 2-0 on the stroke of half-time when he turned in Alvaro Negredo's header from a corner.
Whatever Moyes said at the interval to a United team missing injured striker Robin van Persie had little effect as within five minutes of the re-start City were 4-0 up.
Negredo saw his lofted cross to the far post volleyed in by the unmarked Aguero.
And, in another example of poor United defending, Jesus Navas went unchallenged down the right before his cross was struck home by Nasri.
Wayne Rooney pulled one back for United when he beat fellow England international Joe Hart with a free-kick three minutes from time that gave the striker a record 11th goal in Manchester derbies.
"It was a great win against Manchester United and no-one believes that 4-1 is possible before the game," said Pellegrini.
"We try to be the team that has possession of the ball and creates chances."
Skipper Vincent Kompany believes City were hungrier for the win.
"Maybe the game meant a little bit more to us than for them," said the Belgian.
"It's too early to say it's a defining game. You make a statement over the course of the season."
Moyes admitted United had been out-played.
"We didn't play well enough to win the game. Manchester City played well and deserved the victory," said Moyes.
"If you lose four you are not expecting to win too many. We conceded poor goals. We needed to get closer in the second half but they get away and score more goals.
"We got better as the game went on but it was too late."
Arsenal went top with a 3-1 win over Stoke at the Emirates Stadium and remained there on goal difference after north London rivals Tottenham Hotspur joined them on 12 points following a 1-0 win away to Cardiff.
Wales midfielder Aaron Ramsey made it seven goals in eight games when he gave Arsenal a fifth-minute lead after Stoke goalkeeper Asmir Begovic had palmed away a Mesut Ozil free-kick.
Stoke equalised when United States international Geoff Cameron scored his first goal for the club in the 26th minute from the edge of the box after Marko Arnautovic's volley came back off the post.
Arsenal though were 2-1 up before half-time through centre-back Per Mertesacker's looping header.
Bacary Sagna then made Stoke pay once more for failing to defend a set-piece when he headed home in the 72nd minute from another free-kick by ?42.4 million ($66 million, 50 million euros) club record signing Ozil, the Germany international producing a sparkling display on his Gunners' home debut.
Arsenal manager Arsene Wenger was understandably delighted by Ozil's performance.
"Like the team he (Ozil) gave a lot on Wednesday night (in the Champions League victory away to French side Marseille), but he showed his class today and he worked hard as well," Wenger said.
It seemed Tottemham would have to settle for a goalless draw in Wales until, in stoppage time, Paulinho turned in Erik Lamela's cross for his first Spurs goal.
"Today it was different from normal in that there was justice in football. We created so many chances that there could only be one winner," said Spurs manager Andre Villas-Boas.
"Bearing in mind the win they got against Man City there won't be many teams getting points here so I'm happy."
Sunday's other Premier League match saw Swansea win 2-0 away to Crystal Palace with Michu putting the Welsh club in front in just the second minute before Nathan Dyer added a second goal shortly after half-time.