Chelsea are prepared to trigger Kepa Arrizabalaga's €80 million (£71m/$92m) release clause, with Thibaut Courtois looking to force a move to Real Madrid, Goal understands.
Athletic made it clear that they would not accept any bids for Kepa, meaning that the Blues must meet a price tag in his contract in order to proceed.
It is believed that Chelsea have now agreed to pay the fees required to secure the goalkeeper.
The move would break the club's transfer record, set last season when Chelsea signed Alvaro Morata in an initial £58m ($75m) deal, potentially rising to £70m ($90m), from Real Madrid.