Following a decent run of form in which they defeated Everton, Bournemouth and Juventus by the same 2-1 scoreline, Manchester United collapsed under the incessant attacking might of their noisy neighbours at the Etihad on Sunday.
David Silva's goal in the first half gave City a 1-0 lead going into the break, and Sergio Aguero doubled it shortly after the interval. Anthony Martial briefly gave United hope from the penalty spot, before Gundogan put the result beyond reasonable doubt with less than 5 minutes to go.
Pep Guardiola's men outclassed United in virtually every department, bossing possession, and creating chances for fun. The recent optimism surrounding Old Trafford descended into a familiar cloud of gloom, as the Red Devils surrendered meekly in their 4th loss of the season.
The dismal showing on enemy turf could perhaps be justified by the fact that Jose Mourinho was without his midfield talisman, with Paul Pogba watching on from the stands as David and Bernardo Silva danced around a hapless Nemanja Matic, especially considering that it was the Frenchman who had inspired a memorable comeback at the same venue 5 months ago.
But the harsh truth is that even with Pogba orchestrating the midfield, United have found goals hard to come by, registering just 3 shots on target in the midweek win in Turin.
A blunt attack
Jose Mourinho is a brilliant tactician, and there is absolutely no doubt about that. His teams are built on impenetrable defences and lightning-fast counter-attacks that catch opponents by surprise.
But the game is evolving, and the new breed of defenders that have risen to prominence in the last couple of years are players who can cover a matter of yards in the blink of an eye.
Which is why the likes of Benjamin Mendy, Kyle Walker and Aymeric Laporte had no real issues in dealing with the pace of Anthony Martial and Jesse Lingard on the counter.
In the aforementioned run of victories that United enjoyed, the goals that they scored were more often than not reliant on the volatile brilliance of Martial, Pogba and Juan Mata.
Last season was much of the same, except that Mourinho could always call upon his defence to bail him out after his team had taken the lead. Matic, Smalling and Eric Bailly have looked out of sorts this season, and the result is that United is the only team in the top half of the league with a negative goal difference.
And whenever they attack, there is no semblance of cohesion among the players. The hesitance and indecisiveness on the ball in the final third are down to a lack of identity in attack, a lack of proper tactics.
The United sides of just a decade ago relied on teamwork and chemistry under Alex Ferguson, teams that had quality out wide and were lethal in front of goal. Their attacking tactics were well-defined, a major reason why SAF had that knack of extracting brilliant performances from average players.
Against City, Mourinho chose the brute force of Fellaini, ahead of the guile and creativity of Fred and Mata. The idea was to hurt the opposition through set pieces, and the fact that United rely on such an inelegant way of scoring goals is indicative of their recent decline.
West Brom and Stoke City need free kicks to score goals, not Manchester United.
Nothing to lose
With Mourinho's job on the line though, the one positive to come out of all this mess is that the Portuguese manager knows he has nothing to lose.
He spoke to the media about taking the game to City, and there were flashes of the old United at times when they attacked with abandon on Sunday.
Jose looks like a man who realises that he can no longer depend upon antiquated counter-attacking tactics to bail him out of matches, apart from the fact that his defence looks as flimsy and fragile as that of a relegation contender's.
With the club's board reportedly ready to back him for the moment, expect to see more of that in the games to come.
A change in management looks inevitable by the end of this season at the latest, especially if Mourinho fails to secure a top four spot.
If you're a member of the Old Trafford faithful, don't get your hopes up with respect to the trophies that United could possibly lift in this campaign.
The FA Cup seems to be the best shot at silverware, but Mourinho is heading in the right direction, and that at least should suffice for now.