Manchester City's grip on the Premier League title looks looser than ill-fitting trousers after a slick Southampton side punished a dishevelled display by Roberto Mancini's men. Strikes from Jason Puncheon and Steven Davis, plus a preposterous own goal by Gareth Barry, meant Edin Dzeko's effort counted for little and Manchester United can move 12 points clear at the top of the Premier League with 12 games to go if the beat Everton today.
Having just been crowned champions for the first time in 44 years, City were determined to avoid relinquishing their title within just 26 matches and those, surely, were the stakes here. Roberto Mancini's team started the game nine points behind Manchester United and knew that ceding any further ground to their neighbours would make retaining the Premier League highly improbable. The manager's confidence of avoiding a slip-up at St Mary's was increased by the return of Yaya Toure, who, it was hoped by the visitors, would make the Saints suffer his anger at his country's failure to reach today's Africa Cup of Nations final.
City did not lose any of the five matches that Toure missed while he was away but draws in the last two meant they did lose ground. While Yaya took the captaincy in the absence of the injured Vincent Kompany, his brother Kolo only made the bench, as Javier Garcia partnered Joleon Lescott in defence.
Southampton had to make changes too due to injuries to Luke Shaw and Gaston Ramirez. Danny Fox came in at left-back while manager Mauricio Pochettino chosen to deploy Steve Davis in midfield ahead of the fit-again Adam Lallana. Pochettino has been praised for making a positive impact since replacing the unfortunate Nigel Adkins as manager last month but, despite promising performances, he had yet to guide his team to victory. The Argentinian was hired in the hope that he will propel Saints to the upper echelons of the league but the cheering that greeted the announcement before kick-off that Wigan, Queens Park Rangers and Reading had all lost gave a reminder that the club's immediate concern is averting relegation. Their chances of doing that began to look brighter as soon as the game began.
From the outset Southampton pressed City high up the pitch in the manner that the new manager has demanded. The visitors struggled to match their intensity and were punished on seven minutes, when Puncheon robbed Barry and found Jay Rodriguez at the edge of the area.
Garcia was caught badly out of position but Toure and Hart combined to keep the forward's effort out. The ball broke to Puncheon, who rolled it into the net from 16 yards.
Now City had to show the stuff of champions. They improved enough to force Southampton onto the back foot but not to create clear opportunities. The home team coiled up expertly and then, in the 22nd minute, sprang forward to deadly effect.
Fox instigated the attack with a splendid crossfield ball from the back, which Rickie Lambert trapped before exchanging a one-two with Puncheon and unleashing an 18-yard shot that Joe Hart should have held. Instead the England goalkeeper dropped the ball, and Davis vindicated the manager's decision to start with him by sliding in to poke the ball into the net.
City began to unravel feebly. Rodriguez came close to making it 3-0 when he fired just wide in the 33rd minute, and five minutes later Puncheon blasted into the side-netting.
But just as things were threatening to become humiliating for the champions, they asserted a bit of class, cutting the deficit in the 29th minute thanks to a fine counter-attack. From a Southampton corner they broke downfield before the ever-reliable Pablo Zabaleta crossed for Dzeko to divert it into the net from close range.
Artur Boruc had to intervene to prevent David Silva from equalising before the break but Southampton could have been given a penalty in the 45th minute when Toure leaned into the back of Rodriguez to send the forward tumbling to the ground. This game promised more goals.
Another soon arrived in ridiculous fashion. City were disjointed but few would have foreseen their incompetence sinking to the low they reached in the 48th minute, when Lambert was allowed to canter down the right and send in a low cross that, bizarrely, Barry sidefooted into his own goal.
Barry attempted to redeem himself and clipped a canny ball through to Sergio Aguero in the 55th minute, but Boruc saved the striker's shot.
City needed goals and with Carlos Tevez missing, reportedly for family reasons, Mancini had few ways to boost his attack from the bench. He replaced Lescott with Aleksander Kolarov in the 66th minute and City switched to a back three.
Southampton have surrendered more points from winning positions than any other team in the top flight this season but here they held on comfortably.