Poor performances on road since the 6-1 win at United have dented City's hopes - and it is largely Mancini's faultQ. Manchester City, favourites for most of the season, are five points behind now. Why?
The problem, and the reason that this is likely to be Manchester United's 20th title, and not City's third, is how City are doing on the road. In their last nine away games, City have won two, drawn three and lost four. In those nine games they have scored just five goals, and never more than once in one game.
United, by contrast, have won 10 of their last 12 away games, including victories at Arsenal and Tottenham Hotspur. All season, they have won 12 from 16 away league games. United won yet again on Monday, 2-0 at Blackburn Rovers and have applied enough pressure on City, as they have done on so many title rivals over the years, that they could pounce on the inevitable mistakes.
The run started with a 3-2 win at Bolton Wanderers. Next was a 5-1 thrashing at White Hart Lane of Tottenham Hotspur, the team who had been close rivals in the past two seasons. Even Dzeko scored. Four times. Neither the 2-2 draw at Craven Cottage nor the 4-0 win at Ewood Park were obvious departures from the routine; City have always struggled to hold on to leads against Fulham.
But the 6-1 win at Old Trafford looked at the time like a transforming moment in Manchester football, even if subsequent events have changed that. When City won 3-2 at Queen's Park Rangers in November, it felt like a tight squeeze, but certainly not the end of anything.
It looks as if that game in west London, and the fear that City were conceding too many in away games, has compelled Mancini to overcompensate. He has started to move away from the ambitious 4-4-2, playing 4-5-1 in four of the last nine away games. In those four, City have scored just twice. Returning to last season's tactical plan, he has brought back Nigel de Jong, an expert in destruction but little else, adding midfield protection at the cost of attacking potential.
The full-backs look more cautious, and the result is a more conservative City line-up on the road, so keen to concede fewer that they have lost the knack of scoring many.
But those three have not started together in any of the last six away games, and Mancini has always had to throw in someone else. Yaya Touré went to play in the African Cup of Nations, and James Milner could not replicate his blend of drive and finesse.
Silva has not had a break but might well have benefited from one. He has declined, admittedly from quite a height, in recent months. The physical elements of his game – the touch, the shuffle, the change of pace – have all been blunted and the Spaniard can no longer orchestrate games like he used to. Aguero is showing his own signs of tiredness, too, having not scored on the road since the 6-1 win at United, which feels years ago but was only in October.
Mancini has to ensure that next season he can replicate City's autumn 2011 away form but, this time, sustain it. Part of it will be simple: returning to the 4-4-2 system, with Aguero darting behind a more mobile and enthusiastic target man. Yaya Touré and Silva are both genuine match-winners who, if well managed, can continue to create and score goals – and win games for City on the road.
Mancini might argue that City have been victims of their own success. When West Bromwich Albion dug in for a 0-0 draw at The Hawthorns against City, and got one, other teams might have realised that fighting for a point, even at home, was preferable to gambling on an unlikely win. Certainly, sides hosting City became more cautious as the season went on, with good results.
But management is about meeting emerging challenges and maintaining standards. On this issue, this season, City have squandered their position, and will pay for it.