Despite still being top of the table, City look more vulnerable now than ever.
Unbeaten in the first 14 games of the season, Roberto Mancini's men have failed to win three of their last seven, and the chasing pack will be growing with confidence with every stumble.
A mixture of injuries, suspensions and international call-ups could derail City's great start to the campaign.
Here's a list of signs that show City aren't the unstoppable force they seemed earlier in the season.
Frank Lampard nets the winning goal from the penalty spot
On December 12th, City traveled to Stamford Bridge to play a struggling Chelsea side sitting in fifth place in the table.
Standout performances from Daniel Sturridge and Raul Meireles, however, meant the Citizens headed home empty-handed.
A disappointing defeat was compounded by the sending-off received by Gael Clichy, and they consequently tumbled off the top spot for the first time since mid-October.
Another less than pleasing result for the City faithful, this time against Roy Hodgson's West Bromwich Albion.
The Baggies frustrated the league leaders, and despite having 72 percent possession, Mancini's side failed to break the deadlock.
As a result, they only retained their position at the top of the table on goal distance. If it were not for rivals United's poor form, they may have slipped off their pedestal.
Ji celebrates his winning goal
This was a game City undoubtedly should have won.
A pandemic of poor finishing meant they failed to score for a second game running, and an injury time goal for Dong-Won Ji completed a smash-and-grab victory for Martin O'Neill's black cats.
A win would have extended City's lead at the top with United losing at home to Blackburn, but their rivals stumble went unpunished.
Yaya—the powerful, box-to-box midfielder—has been a linchpin in the City team this year.
A string of impressive performances early in the season firmly cemented his place in the first 11, and his loss to the African Nations Cup is a great one.
Arguably one of the best midfielders in the country, any side would miss a player of his quality, and Mancini will be hoping other players, such as the out-of-favour Nigel de Jong, can step up to the plate.
His brother, Kolo, has come back into the side after returning from a lengthy ban and his absence will also be sorely missed.
Vincent Kompany (far right) starts the long walk back to the changing rooms
A silly challenge in the Manchester derby means Mancini will be without his most influential defender for the next four domestic matches.
A two-footed challenge that divided the opinion of pundits and punters alike will have a substantial impact on City's team.
Stefan Savic has taken the place vacated by Kompany at centre back, but the young Montenegrin has looked jumpy since arriving, and his performance against Wigan on Monday night (16th) was less than reassuring.
Waving an invisible red card at the referee is a gesture that is all too evident in certain European countries.
It is seen as an attempt to directly influence the official's decision, and is widely condemned within not just English but British football.
During City's match away to Wigan, Mancini committed this heinous crime, refusing to apologise afterward and claiming that his actions were no worse than Wayne Rooney's in the Manchester derby earlier in the month.
The incident, as well as showing the Italian's frustration at referee Martin Atkinson's decision, showed that the pressure could be getting to Mancini.
The enigmatic forward has been in good form this season with 11 goals, but his recent injury worries have kept him on the sidelines.
A recurring ankle problem has kept him out of contention for two weeks, with Mario missing most of the Carling Cup loss to Liverpool and the uncomfortable win over Wigan.
Edin Dzeko hasn't been firing on all cylinders lately, and Mancini will be desperate to get the temperamental Italian back in the starting 11.
Richards storms past Arsenal's Gervinho
The powerful full back has been a staple in Mancini's side since the start of the season.
Favoured over Argentinian Pablo Zabaleta, Richards has made the position his own but has only been featured intermittently in the last few weeks as he tried to overcome a hamstring problem.
The England international is a key part of City's team, bombing forward down the right wing, and the fans will be hoping to see him back to his best sooner rather than later.
City fans give us their opinion on the Tevez saga
Since his fall from grace, after refusing to come off the bench in a Champions League game against Bayern Munich earlier in the season, Tevez has been linked with a host of top European clubs.
With Milan's rivals Inter having launched a bid of around £20m, and French club PSG now being linked with the Argentinian, City need to offload the troublemaker in this window and put this fiasco behind them.