Sevilla defender Jules Kounde has already agreed personal terms over a potential future transfer to Chelsea.
The Frenchman was the Blues’ prime centre-back target last summer, but they could not secure an agreement.
They were willing to pay around £42m, but Sevilla were adamant that they wanted at least £55m up front.
The Blues are likely to make a renewed approach next summer, but prior to that, they have a verbal agreement.
The west London giants have been in contact with the player’s agents, and have already agreed terms over a contract.
Rudiger has rejected a new contract beyond June, and has no plans of extending his stay, similar to Christensen.
Azpilicueta’s deal also expires next summer, but the Spaniard is willing to stay if he is handed a two-year contract.
The Blues generally hand 12-month renewals for players above 30, and are reluctant to change their policy for Azpilicueta.