For Chelsea, any successful move for Granit Xhaka - who Sunderland have said is not for sale after rejecting the Blues' £8m bid for the midfielder - would be a radical shift in transfer policy.

Chelsea have fielded the youngest team in the Premier League for the past two seasons and have not not selected a player aged 30 or over during that period. Xhaka turns 34 in September.

Members of the club's leadership, including co-controlling owner Behdad Eghbali, acknowledge that adjustments are needed to improve their recruitment.

Some of the criticism has centred on a perceived lack of leadership and concerns over dressing-room culture, which is something former Arsenal captain Xhaka received widespread praise for helping to build at newly promoted Sunderland last season.

The Switzerland international, who is under contract at the Stadium of Light until 2028, played a key role following a £17m move from Bayer Leverkusen as the Black Cats finished seventh to qualify for the Europa League.

A move for a midfielder has long been part of Chelsea's plans this summer, and comes amid growing expectation that Enzo Fernandez could join Real Madrid.

Chelsea have not received a formal approach for the Argentina international and value him at about £120m. However, sources in Spain suggest there is internal support at Real Madrid for a move, including from club president Florentino Perez and new manager Jose Mourinho.