Tottenham Hotspur are exploring the possibility of re-signing Steven Caulker in the summer – only 12 months after selling him to Cardiff City for £9m.

Spurs have doubts over the future of two of their existing centre-halves, with Jan Vertonghen having attracted the interest of Barcelona and Younès Kaboul set to become a free agent in June.

Caulker was moved on to general surprise last summer, given his status at the time as one of the club's most talented prospects, but Tottenham would take him back if Cardiff were to be relegated from the Premier League and he did not want to stay for a campaign in the Championship. Cardiff are 19th, three points behind 17th-placed Crystal Palace with seven matches to play. It is unclear whether Tottenham have a buy-back clause or the first option on the England centre-half but it is common practice for selling clubs to insist on such arrangements.

Caulker, 22, was born in London and he rose through the ranks at Spurs, breaking into the first-team last season, when he made 17 starts in the league. Tim Sherwood, then the club's youth technical director, pushed for him to make the step up and the manager would be happy to work with Caulker next season.

There remains uncertainty, though, over Sherwood's future and general doubts about the club's direction. The defender Danny Rose said two weeks ago that none of the players knew whether Sherwood would continue as the manager next season and so fulfil the final year on his contract. It is known that the chairman, Daniel Levy, likes the idea of appointing the Holland manager, Louis van Gaal, who will be replaced by Guus Hiddink after the World Cup finals.

There is the sense that Tottenham are in limbo, with Sherwood fighting to prove that he should remain in charge, while the move for Caulker would raise inevitable questions about strategy and joined-up thinking.

On the other hand, Chelsea's re-signing of Nemanja Matic in January for £21m, three years after they allowed him to leave as a makeweight worth £3m in the deal that brought David Luiz from Benfica, has proved that judgments and decisions on players can be reversed. There has been little criticism of Chelsea's buy-back of Matic, largely because of the midfielder's outstanding form.

Vertonghen is on Barcelona's summer shopping list, as is David Luiz, as the Catalans look for a ball-playing central defender. Vertonghen is determined to play in the Champions League and Tottenham, who face Liverpool at Anfield on Sunday, face a huge challenge to finish in the top four. Either way, few players can refuse Barcelona and the Belgian would be a cheaper option for them than David Luiz.

Kaboul will see his contract run out at the end of the season and after two spells at the club which have comprised five and a half years, he will assess his options.