This has been coming, after all.
The relegation-threatened Saints dominated play in every meaningful way. From the point where Southampton took a 1-0 lead in the seventh minute, the Saints had the match by the throat and never let go.
The loss leaves the defending Premier League champions with little left to play for, but plenty of questions.
And a refrain of "When the Saints Go Marching In" echoing in their heads all the way back to Manchester.
Players are graded on a scale of one (watching United lift the trophy in May...it's coming) to five (how it used to feel to watch the Citizens play).
Joe Hart: There are few words to describe how dodgy Hart was in this match. But his mishandling of Rickie Lambert's strike in the 22nd minute that allowed Steven Davis to slide in and put Southampton up for good was the stuff of blooper reels. 1.
Pablo Zabaleta: Zabaleta is the only City player who will be able to look himself in the mirror after this match. His runs up and down the right flank sparked his side's only real threats on the day, and his assist on Dzeko's goal was timely, if not beautiful. 4.
Joleon Lescott: It is shocking to see how far Lescott has fallen off from last season's level. Without Vincent Kompany and Matija Nastasic, City needed a huge game from Lescott. But he was hapless on the first two Southampton goals, and he'll be heading back to the bench as soon as Kompany or Nastasic is fit. 1.5.
Gael Clichy: Where Zabaleta's forays upfield had purpose, Clichy's efforts lacked direction and produced negligible results. Clichy is becoming harder and harder to hide back there. 2.
Javi Garcia: This rating would be lower, but Garcia is playing out of position as a center back. The only hope was that City would get a lead and then be able to switch a defender on for Garcia and push him forward. But, of course, that never happened. Garcia looked unsure for much of the day. 2.
Yaya Toure: City fans had to be excited to see Yaya on the team sheet. But he left his game somewhere in central Africa. Yaya was lumbering and a step (or two) behind all day. His play made a difference, all right, but it was the wrong kind. 1.5.
Samir Nasri: At this point, it is doubtful that Nasri could start for Arsenal. Heaven knows the Gunners would not buy him back. If City suffers a housecleaning at the end of this disappointing campaign, Nasri is probably the first one out the door. 1.5.
Gareth Barry: In ice hockey, plus/minus is a statistic that counts the goals a player is on the ice for, both for his team and against his team. Barry played the whole game, had a shameful own goal and contributed mightily to the first Southampton goal. The ice hockey plus/minus stat thus fits here. -2.
David Silva: Even the little magician seemed to leave his top hat and wand on the team bus today. Many people may not have noticed it, but it was his indifferent play of a free kick in his own half that eventually became the first Southampton goal. When Mancini substituted Silva off in the 73rd minute, it was a message sent to Silva and the whole side. 2.
Sergio Aguero: With Mario Balotelli long gone and Carlos Tevez unavailable, City needed a big performance from Aguero. But City got no such thing from Aguero, who rarely threatened and was often easily neutralized by Southampton's defenders. Service to Aguero was poor all day, for sure, but then Aguero is supposed to be able to make his own chances. Not in this one, he didn't. 1.5.
Edin Dzeko: But for Dzeko's professional control of Zabaleta's imprecise cross, City would likely have been shut out in this one. Dzeko's performance on the day was pretty mediocre, but he scored a goal and that is his job. 3.
James Milner (56th minute for Nasri): By the time he came on, it was nearly too late for Milner to make a difference. Milner was workmanlike, but with his side down 3-1 on the road in the second half, industrious play was not really what was needed. 2.5.
Aleksandar Kolarov (66th minute for Lescott): Just about anyone would have been an improvement over Lescott. Kolarov, unfortunately, was exactly that: Just another hapless Sky Blue mopping up a hapless day. 2.
Maicon (73rd minute for Silva): Maicon entered a hopeless match that ended the same way he found it. No rating.
Roberto Mancini: Fox Soccer's talking heads accused the City players of quitting on Mancini against Southampton. That's a tad silly. It is not Mancini's fault that Yaya was gone for a month (and played terribly today), that Hart fumbled an easy save into a goal and that Kompany has missed so much time. Even an expensively-assembled squad like this one can lack cohesion under such circumstances. That they played like strangers against Southampton is just not Mancini's fault.