Manchester City have spent over €130m this summer but, given the length of time it's going to take the team to adapt against the actual upgrade – or not – in quality, is it worth it? We compare Roberto Mancini's new men against the players they're likely to replace

Joe Hart v Shay Given

Okay, Hart is a loan return rather than actual signing but, if it means City miss out on the Champions League again, it could end up being more expensive than anything their largely irrelevant accounts say. Goalkeeper, after all, is a little too important a position to take such a gamble on. Now there's no denying that Hart has most of the attributes to be a top-class goalkeeper and he has illustrated them throughout most of his recent career. Examining a basic stat too, he had a marginally better saves-to-shots ratio than Given last season (77% against 73%) but both were in the Premier League's top seven. And that's the point. It was marginal. Is it enough to replace an experienced goalkeeper who's proven himself under top-four pressure with a largely untested one who hasn't?

Much of the praise being lavished on Hart now was also lavished on Ben Foster until September 2009 when, ironically in a game against City, he got a proper taste of what's required at a club that's actually competing. Arsene Wenger may have a fair few issues with his own goalkeeper but he's right when he argues that any age under 26 is far too young to mind the net for a big club. At just 23, we don't yet know how Hart is going to respond to that tension over a long period of time. With Given, we know exactly. Keeping Given the number-one for at least another season would have appeared the more logical decision.

Jerome Boateng v Pablo Zabaleta

A definite enhancement but we're not exactly talking an Atari to an X-Box here. Adaptable and assured, Zabaleta is the sort of full-back you don't notice too often because he rarely does anything too disastrous or too spectacular. In short, he generally just does his job. Boateng's physique and energy make him pretty difficult not to notice, however, even if those attributes and the positions they allow him to get into should mean he gets more goals and assists from open play. Generally as dependable in defence as Zabaleta – even if Boateng could have nightmares about Andres Iniesta for years after the World Cup semi-final – the key difference here is the extra dimension he gives on his forays forward. A staid City often lacked that extra angle last season.

Aleksandar Kolarov v Wayne Bridge

It would be harsh to judge Bridge's present qualities on last season. But then we're not exactly expecting sentiment from City. In any case, it's probably a correct call. As Bridge's career history illustrates, he's capable of bringing both himself and his club to a particular level before reaching a plateau thereafter. Just like when he initially signed for Chelsea in 2003, Bridge is a good enough player to make a first statement, not enough to make the next step. A little like choosing Boateng over Zabaleta, the "attack-minded" Kolarov should give City that badly-required extra width going forward. There's also an awful lot more to his game, including a rocket of a left foot. Despite the near-€20m fee, he probably acts as one of City's better pieces of business in the summer.

Yaya Toure v Nigel De Jong/Gareth Barry

Granted, City started with the three of these players in the middle against Tottenham – as they're likely to in all of their difficult away games – and may well do the same against Liverpool. But, at home against lesser opposition, James Milner is surely set to drop back to allow an attack of Carlos Tevez, Mario Balotelli and David Silva, meaning one of De Jong or Barry is going to miss out.

The theme of Mancini's summer appears to have been greater mobility and he will clearly have been seduced by some of the surges Toure made from deep for Barcelona. That was for a set-up a lot more fluid and conducive to that kind of play than City. Otherwise, there are worrying lapses in Toure's discipline and it should be disquieting that Barca – a team whose level City aspire to – so readily discarded Toure because Sergio Busquets could do his job much better. Barry has been steady without being spectacular for City – and never as bad as his World Cup would lead you to believe – but De Jong has really matured over the last year and, on present form, is superior to Toure. Much will depend on whether the Ivorian can provide the extra drive but this was probably one of the areas of the team Mancini didn't need to touch.

James Milner v Adam Johnson

Again, this depends on how Mancini sets out his team but appears the likeliest alteration. You'd forget there's less than half a year between these two given how Milner appears the finished article and Johnson an exciting work-in-progress. But, despite the different approach Johnson's craft gives City, it's hard to argue in favour of his potential over Milner's productivity. The former Villa man provided a goal or assist once every two games last season, Johnson once every three.

David Silva v Craig Bellamy

The real reason Mancini got rid of Bellamy is all too apparent but is Silva's inconsistency really the solution? His undoubted talent is offset by fragility and, although now the holder of European Championship and World Cup medals, the suspicion he was carried by the rest of Spain's attack was confirmed when he lost his place in South Africa. There was little to choose between their output last season as both provided either a goal or assist every two games. Silva did so amidst highly erratic excellence, Bellamy through thoroughly honest endeavour. A team with so many new individuals arguably need more of the latter.

Mario Balotelli v Emmanuel Adebayor

Two players clearly possessed of astounding natural talent but also astoundingly difficult personalities, Balotelli probably shading both. It's which way the scales tip that's going to determine whether this works out or not. There is one huge item of evidence in Adebayor's favour though. Balotelli may very well be Mancini's man but it's a massive mark against him that a man-manager as renowned as Jose Mourinho – who generally makes even the biggest egos fall in love with him – effectively deemed the young Italian unmanageable. We're likely to see as many displays of petulance as pure class from him. Adebayor may not have impressed with some of his actions in the past but since 2007-08 he's maintained a record of over a goal every two games.