Manchester City have already carefully mapped out their transfer plans for the next 18 months and have prioritised signing a top class defensive midfielder and centre-half as well as Arsenal striker Alexis Sanchez as they target serial success under Pep Guardiola.

City will only move for Sanchez in next month’s transfer window unless circumstances absolutely demand it and prefer instead to wait until the summer to sign the Chilean, with Guardiola worried about unsettling the attacking balance in his team and dressing room harmony in pursuit of the Premier League title.

There are thought to be particular concerns about how Argentina striker Sergio Aguero would react if Sanchez arrived in mid-season and, beyond that and the wider harmony of the group, Guardiola believes the form of his front players, especially Raheem Sterling and Leroy Sane, has reduced the need for an imminent move for the Arsenal forward. City are currently 11 points clear at the top of the table.

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Txiki Begiristain, City’s director of football, held a planning meeting with chief executive Ferran Soriano and chairman Khaldoon al-Mubarak last Friday (Dec 15), at which they ironed out their transfer strategy for the next 18 months. City are refusing to entertain any quick four or five month fixes and are determined to ensure they guard against a repeat of a situation such as last summer, when they lost four full-backs in one go.

If City do business next month, it is likely to focus on the recruitment of a central defender, with Southampton’s Virgil van Dijk a preferred target ahead of West Bromwich Albion’s Jonny Evans and Inigo Martinez, of Real Sociedad.

City have already been in formal contact with Southampton, not least to ensure they avoid a situation like Liverpool encountered last summer when the Merseyside club were reported to the Premier League by their South Coast rivals for an alleged illegal approach for Van Dijk. It is thought Southampton are more open to selling the Holland defender next month than they were in the summer but their £70 million price-tag is considered prohibitive, despite interest from Chelsea and Liverpool ensuring his valuation remains high.

City tried and failed with a £21 million bid for Evans in August, but while they have not discounted another move for the Northern Ireland defender, they have yet to re-establish contact with West Brom for the 29-year-old, who is wanted by Arsenal. Any central defensive recruit would be third choice behind Nicolas Otamendi and John Stones as things stand. City have no current plans to sign another left back, though, with Guardiola satisfied by the progress made by Fabian Delph and hopeful of having Benjamin Mendy back from injury in April or May. Danilo and Oleksandr Zinchenko can also provide cover there.

However, City’s powerbrokers do consider the purchase of a defensive midfielder – or European style No. 6 – a necessity next summer given that Yaya Toure is expected to leave the club when his contract expires at the end of the season and Guardiola is overly reliant on Fernandinho, now 32, in the position. Julian Weigl, the Borussia Dortmund and Germany midfielder, 22, is one player City have scouted for that role. Fernandinho, out of contract in the summer, will be given a new deal but Guardiola wants more competition for the Brazilian.

Guardiola’s eagerness to sign Sanchez remains strong, too, despite City pulling back from their initial plans to move for the player in January following the collapse of a £60 million bid in August.

Although aware that Europe’s top clubs will be able to make counter approaches for Sanchez from Jan 1 and Arsenal would prefer to sell overseas, City are confident that the 29-year-old’s desire to move to the Etihad Stadium is strong enough that they can take a calculated gamble by waiting until his contract expires in June before making their move. Bayern Munich and Paris St-Germain have also been linked with Sanchez.

City could still face a predicament then with Aguero but would prefer to deal with any potential fall-out in the summer than during the campaign with so much at stake now. It is understood City have no plans to sell Aguero and will not make any attempt to force out a player they regard as a club legend and whom the supporters idolise. Some at the club even before Aguero’s peak years are still to come but the situation could come to a head in the summer should Sanchez arrive, as expected.

Aguero is the favourite player of Guardiola’s son, Marius, and the City manager had always made it his intention to improve the Argentine’s all round game but their relationship has been strained. Only last Saturday Aguero threw down his gloves in frustration and refused to look at Guardiola after being substituted for Gabriel Jesus with 33 minutes left in City’s 4-1 win over Spurs. Guardiola believes Aguero has benefited from the competition provided by Jesus’s arrival last January but he has already admitted he finds it difficult to accommodate both players in his starting line-up and that issue will become even more complicated if Sanchez joins.