With Manchester City's squad in need of overhaul, who stays and who goes?

Throughout their transformation from Premier League mid-table also-rans into regular title challengers, Manchester City have been a pure buying club.

This is hardly a revelation: Sheikh Mansour's millions have unquestionably been the major reason they have become one of England's leading sides.

Yet the nature of their transfer activity has nevertheless been unusual. In that they've never sold a single key player, with the likes of Carlos Tevez and Mario Balotelli sold at times when they were not fundamental to the cause.

The likes of David Silva and Yaya Toure arrived before City were even a Champions League side and have been regulars since. This is not a club that is accustomed to rebuilding.

In one respect, that's what you'd expect for a major club. Yet last summer, for example, Bayern lost Toni Kroos and Mario Mandzukic, while Barcelona allowed Alexis Sanchez to join Arsenal and Victor Valdes departed at the end of his contract and Real Madrid sold Xabi Alonso and Angel Di Maria to make room for others.

Some of these losses were major setbacks and some were calculated gambles but the effect was similar: it forced others to step up and take responsibility. At City, on the other hand, nine of the 11 title winners from 2011-12 are still regulars.

The rebuild for next season must start with a couple of significant sales. Who might be on the way out?

Joe Hart

Hart was the Premier League's best goalkeeper during Manchester City's 2011/12 title-winning side, but his form dipped dramatically over the next couple of seasons. Last summer's signing of Willy Caballero seems to have prompted a resurgence, however, and City will consider themselves lucky to have two top-class goalkeepers. Still popular with fans and one of the symbols of this City, it's tough to see him departing this summer.

Pablo Zabaleta

Another popular member of the side, the right-back's struggles this season have nevertheless been worrying. Following his run to the World Cup final with Argentina last summer, Zabaleta has looked exhausted frequently this season, which is a huge problem. In reality, he is neither a top-class full-back defensively, nor a particularly talented player going forward, but he's been capable of doing both reasonably well because of his incredible energy. If he no longer has that stamina, he's on the way down. Now 30, and with 12 complete seasons of football under his belt, a dip is imminent, although he probably deserves another season to prove us wrong.

Vincent Kompany

Kompany's mistakes this season have been well-documented, but it would nevertheless be a bold move to sell the Belgian. In a team supposedly lacking clear leaders, City's captain remains a major presence and it's not like anyone else is ready to replace him at centre-back, with Eliaquim Mangala unconvincing and Martin Demichelis now 34. Nevertheless, if City received a huge offer, they might be tempted. The question, however, is who would offer silly money? PSG and Real Madrid are well-stocked for centre-backs while Barca are under a transfer ban and are reluctant to pay top dollar for a defender in any case. He seems likely to stay.

Gael Clichy/Aleksandar Kolarov

These two have shared full-back duties over the past five seasons and have provided useful tactical variety -- Clichy is neat, tidy and gets through his defensive work efficiently, while Kolarov is more attack-minded and boasts a tremendous left foot. Both are now 29, however, and considering City's major problem is the high average age of the squad, it makes sense to release one, and purchase a youngster who can gradually become a regular. Clichy could be the one to depart. 

Yaya Toure

The most obvious candidate to be sold. At his peak Toure is the complete midfielder, yet his form has dipped since last season, and his frustrating lack of work rate often symbolises City's sloppiness -- he sprints forward into attack, then jogs back into defence. True box-to-box midfielders -- and potential replacements -- like Arturo Vidal or Paul Pogba of Juventus do both with great intensity. Time may be up for Toure, who will be 32 this summer, although with two years remaining on a contract that pays him in the region of £200,000 per week, City might struggle to shift him. 

David Silva

The man who makes City tick, Silva has been in outstanding form this season and has finally added goals to his game too. With the major Spanish clubs sorted for playmakers, and four years left on a contract signed at the start of this season, there's no reason for him to leave the Etihad Stadium.

Samir Nasri

A curious case, he is rarely City's star and not someone considered a major figure in the dressing room, but nevertheless is a quietly efficient and versatile performer in midfield. He seems likely to stay, simply because it's difficult to imagine who would come in for him. For example, a move to PSG might be controversial due to his history at Marseille, although Nasri does have a fondness for Italian football, so Roma is a potential destination.

Sergio Aguero

Like Silva, he's a man City can't afford to lose. He guarantees goals and his form at the start of this season was the best of his City career.

Edin Dzeko

There have been rumours of his departure almost every transfer window but this summer might finally be time. The signing of Wilfried Bony, who is nearly three years younger and has a better scoring rate, suggests City are looking elsewhere. There would be no shortage of takers for Dzeko, with a return to Germany, or a move to Italy, most likely.

Squad players

Other departures are certain. Frank Lampard's contract will expire and he'll finally join New York City FC, while Stevan Jovetic's omission from the Champions League squad suggests a return to Italy is imminent. And though Manuel Pellegrini has repeatedly sung James Milner's praises, the longer he goes without renewing his contract, the more he seems destined to leave.

Players like Fernandinho, Caballero, Demichelis, Mangala, Bony and Bacary Sagna are probably safe for various reasons, though Jesus Navas' and Fernando's futures will depend upon the identity of City's next manager as they're the type of players who might not fit into a particular system.

That, of course, is the other looming big decision: Do City keep Pellegrini? There's no doubt that this squad requires a significant overhaul, primarily because of its age, and yet these players are on such expensive contracts that they'll be difficult to shift. In those situations, owners often choose the easy option, which is simply to change the manager.