While not discussing the status of the transfer, Chelsea coach Maurizio Sarri said that Kepa was "very young, but very, very good".
"For me, Courtois is one of the best", he said on Sky Sports'Premier League launch show. "It's an accumulation of things, and I am very glad Chelsea has made a decision to trust me and to take me in as well".
"He has already demonstrated fantastic quality and consistency and will be a big part of any success Chelsea have in the coming years", Chelsea director Marina Granovskaia said.
Mateo Kovacic has revealed how he sought the advice of his Croatian and Real Madrid team-mate, Luka Modric, before sealing a loan move to Chelsea for the upcoming season.
With Arrizabalaga's arrival, the Blues are expected to sanction the departure of Courtois, who has been constantly leaning towards a Real Madrid move.