A magnificent Manchester City display earned them a 4-1 derby-day home win over Manchester United on Sunday, and second spot in the Premier League.
Argentina striker Sergio Aguero led from the front for City, volleying home acrobatically in the 16th minute and adding his second amid a glut of three goals in a five-minute span either side of halftime.
While it was the signature victory City really needed to kick-start the Manuel Pellegrini era, United will be reeling after being embarrassed at times by its neighbor just when the team appeared to have clicked under new manager David Moyes.
Wayne Rooney curled a free kick into the top corner in the 87th minute - becoming the highest scorer in Manchester derbies with 11 goals - but that will be little consolation to the England striker or United, which fell five points behind early pacesetters Arsenal and Tottenham after five matches.
City climbed to third and has now scored seven goals in two matches, on the back of a 3-0 win over Viktoria Plzen in the Champions League on Tuesday. The influence of Pellegrini may finally be kicking in.
It equaled City's biggest home win in the derby since a mauling by the same score line at the Etihad Stadium in 2004, and when Nasri volleyed in the fourth goal after 50 minutes, memories came flooding back of the 6-1 beating City handed its neighbor at Old Trafford in 2011.
While that was a freakish result - against 10 men in part - this was fully deserved and even more dominant.
The only consolation to the visitors was that they didn't concede any more.
The absence of striker Robin van Persie - sidelined by a groin strain - was a major setback for United, with the Dutchman having linked up smoothly with a revitalized Rooney so far this season.
Rooney missed his strike partner and had a frustrating match, smashing a ball into the side of the prone Aguero after giving away an early free kick and then picking up a booking later in the first half for hacking at Vincent Kompany's legs. His late goal, great as it was, will largely be forgotten.
That exasperation had built up because of City's sheer dominance all over the pitch, particularly in midfield where Toure, Fernandinho and the impressive Nasri had total control.
It was Nasri who set up the first goal, flicking the ball deftly into the path of Aleksandr Kolarov for the left back to fire over a cross that Aguero hooked in spectacularly.
It took United 42 minutes to have its first shot - Antonio Valencia dragging wide - and the visitors were further behind at the break when Alvaro Negredo headed down Nasri's corner to the feet of Toure, who bundled the ball in from close range in injury time.
It was the best City had played all season, outstripping its display in the opening-weekend 4-0 win over Newcastle simply because of the quality of opposition they were facing and reminiscent of the displays they produced most weeks in their title-winning 2011-12 campaign.
And when Aguero volleyed in from inside the six-yard box after good work by Alvaro Negredo, a repeat of the hiding City gave United in its own ground two years ago looked on.
That didn't prove to be the case but United's players couldn't get off the pitch quicker at full time.
