Kepa, who joined the Basque club at the age of nine and has been first choice since the 2016/17 season, is now expected to fly to London after already agreeing what AS reported as a 'five or six' year contract that Marca explained was negotiated with Chelsea via a third party mediator.
It is expected that 23-year-old Kepa will undergo a Chelsea medical when he arrives in London, before the transfer, a new world record for a goalkeeper, is confirmed.
Chelsea manager Maurizio Sarri is thought to want Kepa to start training with his new teammates on Thursday, with a view to selecting the Spaniard for the opening game of the 2018/19 Premier League season against Huddersfield on Saturday.
His arrival at Stamford Bridge will allow Thiabut Courtois to complete a move to Real Madrid.
The Belgian failed to report for training earlier this week in a bid to force an exit from the club, leaving Chelsea little choice but to move heaven and earth to find a replacement in the incredibly short timeframe before the imminent Premier League transfer deadline.