David Moyes's first derby as Manchester United manager turned into a nightmare on Sunday as Manchester City inflicted a humiliating 4-1 defeat at a triumphant Etihad Stadium.
With Robin van Persie absent due to a groin strain, a limp and lacklustre United were dominated from kick-off on a sunny afternoon in northwest England.
They saw City take control through first-half goals from Sergio Aguero and Yaya Toure, and quick-fire strikes from Aguero and Samir Nasri in the second period meant the game was over after only 50 minutes.
Wayne Rooney scored a fine late free-kick to become the outright leading scorer in the fixture, but it could not stop City's fans revelling in a victory almost as seismic as their 6-1 win at Old Trafford in October 2011.
That victory paved the way for City's subsequent title triumph, and after a dream first derby as manager, Manuel Pellegrini saw his side climb to third place in the Premier League table, two points behind leaders Arsenal.
Defending champions United, meanwhile, find themselves five points off the pace after two defeats in their first five games.
Moyes can console himself that his storied predecessor Alex Ferguson once lost 5-1 at City, but from three games against title rivals City, Chelsea and Liverpool, his side have picked up just a single point.
Van Persie had scored the winning goal in last season's corresponding fixture and his unexpected absence from the United team-sheet was the first indication that it might be City's day.
Danny Welbeck was the beneficiary, with Ashley Young also coming into United's team, while Pellegrini chose Alvaro Negredo over Edin Dzeko in attack but was unable to select David Silva in his squad due to injury.
United began with purpose, Welbeck charging down an attempted clearance by Vincent Kompany inside 10 seconds, but the hosts quickly took control before striking in the 16th minute.
With Antonio Valencia dawdling, Aleksandr Kolarov hared onto Nasri's cute back-heel and crossed from the left for Aguero to hook home a smart left-foot volley from eight yards.
Despite the presence of the giant Marouane Fellaini, United were swamped in midfield and saw Nasri lash a sweetly struck volley narrowly over David de Gea's crossbar moments later.
United's frustration told in a booking for Rooney for a succession of offences, culminating in a hack at City skipper Kompany, and it got worse in first-half injury time when Toure made it 2-0.
Nasri's corner was headed down by Negredo and the giant Ivorian had the freedom of the six-yard box to knee the ball over the line from close range.
Moyes elected not to make any personnel changes at the interval and within 62 seconds of the restart, his side fell further behind.
The irrepressible Nasri was again the instigator with a pass down the inside-left channel for Negredo, who held off Nemanja Vidic, swivelled, and crossed for Aguero to volley in his second of the game.
Within minutes it was 4-0, the unmarked Nasri volleying in a cross from Jesus Navas, who had been allowed to run 80 yards unchallenged.
The Etihad dissolved into a mass version of the backwards-facing 'Poznan' dance beloved of City's fans and only sharp defending from Vidic prevented Negredo from adding a fifth.
After Patrice Evra hit the post with a late header, Rooney planted a fine 25-yard free-kick into the top-right corner to claim a record 11th derby goal, but it provided meagre consolation.