Garry Cook has that smile on his face. So does Roberto Mancini. It's Thursday evening, 24 October. Manchester City have just beaten Lech Poznan 3-1 in the Europa League. Even better, that win is part of a streak. Four on the bounce in the Premier League, including a victory over the champions, Chelsea. They're undefeated since August and it's a run that's left them second in the table. More importantly, it's left them above United. Best of all though, they're about to push their great rivals down further. Potentially permanently. Cook has apparently been informed that the financial package City are putting together will be enough to entice Wayne Rooney. The sound in the background is the earth moving, the landscape changing. And City have the higher ground on a mountain of money. Oh, they're smiling at Eastlands alright.

Little more than 12 hours later and they're not smiling. They're smarting. Cook is said to be "furious". One City official is "hurling things around the room". They've just got the call. Rooney is staying at Old Trafford. They had been sure they had both him and the future superiority of the city itself. Two days later, United claim an unlikely late win against Stoke City thanks to Javier Hernandez. The Mexican's undoubted qualities notwithstanding, he's the sort of "value buy" – as Alex Ferguson has put it – United have resorted to in the absence of the financial resources to compete with their neighbours. About an hour after that, Dedryck Boyata is sent off at Eastlands against Arsenal. Down to 10 men, City hold strong but eventually unravel. And keep doing so. They lose to Wolves and fall further behind United. Poznan then reverse the 3-1 scoreline on Tursday in Poland. That sound is no longer the landscape splitting but, supposedly, City themselves.

They go into today's tricky trip to West Brom and Wednesday's tinderbox Manchester derby not looking to shake things up but just about hold it together. The authority Mancini sees as so important to assert is becoming one of the biggest problems for his squad. Some reports have it that a core of players are close to mutiny. Whatever the truth of that, it all only means that City look a lot less assured than they were 16 days ago. Heaven can wait. Heaven must wait.

It would be a huge stretch to argue that Rooney's eventual decision that morning and City's sudden slump are connected. For a start, one of football's oldest clichés advises not to take much evidence out of the first 10 games of the season. And City are unlikely to have been the bona fide contenders they appeared in the opening eight. As Roque Santa Cruz even admitted at that time "we are below the level of those who will fight for the title". The longer a season goes on, after all, the likelier it is a team's various strengths and weaknesses balance out.

But even the notion of Rooney arriving could have bolstered City's mentality and dramatically altered the dynamic of this week's derby. It might have also added momentum. Instead, the vacuum left has allowed some of the potential problems that are inherent at a nouveau riche club like City to start playing out. A dressing room filled with difficult, precious characters has begun to look exactly that. And the lingering questions over whether Mancini really was the right man to replace Mark Hughes have returned with a bit more cutting edge. Because, to an extent, that's what it keeps coming back to. Does his ability match the bosses' ambitions? We still don't know.

Much like City as a team though, it's too early in Mancini's career to tell exactly how good he is as a manager. There are too many caveats to a competent CV. Yes, he's managed three of Italy's so-called seven sisters – Fiorentina, Lazio and Inter. But even that first job came about through character references from the likes of Sven Goran Eriksson rather than qualifications or achievements. And, equally, it's been hard to extract the actual events from the image thereafter. His time at Fiorentina, for example, will show a Coppa Italia win, a ninth-place finish and then a dramatic slide into the relegation zone... but it's obscured by the tear-gas that engulfed his last fixture as the club's ruinous finances were revealed and the fans rioted. At Inter, it was the opposite. His club thrived while the rest of Italy struggled to survive. Indeed, many did so by selling their best players to the San Siro, further tilting the playing field. Which begs the question as to how much of Inter's achievements could be attributed to Mancini? Not for nothing does the period continue to be known as "Moratti's revenge".

To use an unfair example but one that City's owners undoubtedly crave, however, Mancini never took all that money to the next level in the manner Jose Mourinho did. And, as such, he can so far be labelled an effective manager but not an exceptional one. Words that also apply to his team. Right down to their functional formation.

Much was made of City's win over Chelsea but, rather than a statement of intent, it appeared no more than a re-assertion of the club's Indian sign over the English champions. Mancini has set them up in such a way that they are competitive against the better teams and hard to break down, but too cautious elsewhere. Indeed, his 4-3-3 appears almost entirely dependent on Carlos Tevez's incisiveness. The Argentine has, after all, scored almost half (45 per cent) of the team's goals since Mancini took over and over half (54 per cent) this season. The manager's effective unwillingness to let other players join him as freely was the root of their row against Newcastle. Yet, once Mancini was forced to alter his system in Tevez's absence to a 4-4-2, he found his players couldn't adjust. They were toothless against Wolves. More damning, Mancini couldn't explain why.

Anyone else could hazard a guess though. So hard does Mancini work on one particular formation in training that the flexibility he craved in the last two league matches did not naturally follow. He conceded as much himself. "Maybe it could be this change that made us lose our balance."

If so, it's a rare – and ironic – instance of Mancini's notorious discipline actually having an effect. Because when he's tried to instil it off the pitch so it's actually beneficial, he's suddenly found his rules flexed. And some of his players' arms flexed as they threw back drink at a student party. Amusingly, there was understood to be complete bafflement amongst Mancini's continental staff as to why men around their 30s like Gareth Barry and Shay Given would want to even appear at a student's party in Edinburgh, as they did during the week.

The repercussions of that have been misconstrued as a mutiny against Mancini. That's undoubtedly overstating it though. Yes, there are a few among the City squad that openly dislike Mancini. There are many more who see him as distant, more a martinet than a mentor. Among them are those that have worked with him longest like Patrick Vieira. But the reality of City's situation seems to be that, rather than a club in crisis, they are merely a collection of varied but valuable individuals, some of them with worryingly difficult personalities. They need a strong manager, much like Mourinho was in his first season at Chelsea. Fundamentally, Mancini isn't yet at that stage and may never be. So the squad always seems on edge, ready to spill over. The ultimate example of that is its captain. Tevez is in rampant form but his very mentality makes him, at present, unreliable. City have at least been boosted with the news that he could return to action either today or in the derby.

That may provide them with the temporary boost and sense of momentum that Rooney's signing would have. The feeling is that, against a United side with their own Indian sign over City, Mancini's team are going to need everything they can get. Many hoped Rooney would be the man to finally see them overtake United. Without the striker, Mancini has got to start proving that he is.

FA Premier League: Manchester City v Manchester United, Eastlands, Wednesday, 7.30, Live, Sky Sports 2, 7.00

Carlito's way Tevez's net gains

Since Mancini took over, Carlos Tevez has been almost indispensable for Manchester City. Of the four games they have started without him in that time, the club haven't won a single one. As their paltry return of three goals in those games indicates, Tevez has taken on the majority of the goalscoring responsibility.

45% Percentage of City's league goals Tevez has scored since Mancini took over

54% Percentage of City league goals Tevez has scored this season

mdelaney@tribune.ie