Sunderland say experienced midfielder Granit Xhaka is not for sale after it emerged Chelsea have entered talks with the player's camp over a potential move.
The Switzerland international, 33, who is under contract until 2028, played a key role in helping the Black Cats qualify for Europe last season.
His representatives are understood to have had contact from Stamford Bridge - though sources inside the club have yet to confirm it.
But he is known to be open to a reunion with former manager Xabi Alonso at Chelsea, having won the Bundesliga together with Bayer Leverkusen in 2024.
Personal terms have not been agreed with Chelsea, however.
Sunderland qualified for the Europa League at Chelsea's expense on the final day of last season and are known to have no financial pressure to sell key players. Sources at the club say they have no intention of letting Xhaka go.
The ex-Arsenal man - who is with Switzerland at the World Cup - missed just four league games for the Wearside club and won plenty of plaudits as he captained Regis Le Bris' side to a seventh-place finish.
For Chelsea, any successful move would see a radical shift in transfer policy, signing a player who will turn 34 in September, having fielded the youngest team in the Premier League for the past two seasons. They have not selected a player aged 30 or over during that period.
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 the former Arsenal captain received widespread praise for helping to build at newly-promoted Sunderland last season.
A move for a midfielder has long been part of Chelsea's plans this summer, and comes amid growing expectations that Enzo Fernandez could join Real Madrid.
Chelsea have not received a formal approach for the Argentina international and value him at around £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.
Chelsea are also set to sign Atalanta right-back Marco Palestra, while a number of players — including Alejandro Garnacho, Liam Delap, Malo Gusto, Trevoh Chalobah, Wesley Fofana and Tosin Adarabioyo — face uncertain futures.
Defender Marc Cucurella has already joined Real Madrid.


Ticket Chaos Leaves Hundreds of Ghanaian Fans Stranded Outside World Cup Stadium
Asantehene Warns PSGH: “Expand, But Never Compromise Standards”
Empower the Youth Through Arts to Save Ghana’s Culture — KNUST Lecturer
BoG Governor: Ghana’s Recovery Proves Africa Must Build Stronger Domestic Debt M...
China Throws Full Support Behind Ghana’s Energy Independence Drive
“Stop the Live Bullets Now”: MP Cudjoe Warns Festival Gunfire Is Becoming Deadly
“No One Is Above the Law”: NPA Boss Says Ken Ofori‑Atta Cannot Escape Accountabi...
“Ghana Isn’t Asking for Charity—It’s Open for Business”: Kwamigah-Atokple Makes ...
Mahama Wraps Up Central Region Tour with High‑Energy Apam Town Hall, Pushes 24‑H...
Mahama Breaks Ground on Assin Bereku 24‑Hour Market, Supercharges Central Region...