Chelsea completed the club-record signing of Kepa Arrizabalaga on Wednesday, hours after Athletic Bilbao confirmed the trigger of his €80 million (£71.5m) release clause, making him the world's most expensive goalkeeper.
The 23-year-old signed a seven-year contract at Stamford Bridge, shortly after Chelsea confirmed a deal had been reached to grant Thibaut Courtois his desired move to Real Madrid.
Chelsea were forced to scramble to find a new first-choice goalkeeper in the final days of the Premier League transfer window after Courtois declined to report at Cobham for training on Monday, instead choosing to remain in Belgium and exert pressure on the Blues to sell him to Madrid.
"It's a very important decision for me, for my career, and also for my personal life," Kepa told Chelsea's website. "So many things attracted me to the club, all the titles the club has won, the other players, the city, the English Premier League. It's an accumulation of things, and I am very glad Chelsea has decided to trust me and to take me in as well."
The buyout clause eclipses Chelsea's previous record transfer fee, the €65.5m (£58m) they paid Real for Spanish striker Alvaro Morata last summer.
Breaking the bank for Kepa is a drastic change of direction for Chelsea, having lost out to Liverpool in the race for Brazil No. 1 Alisson earlier this summer because of their reluctance to meet Roma's valuation of the player, who ultimately moved to Anfield for £56m.
Kepa was close to joining Real Madrid for as little as €20m in January, but the deal was blocked by then-coach Zinedine Zidane, and Athletic responded by committing their prized asset to a new long-term contract, which increased his buyout figure to €80m.
Athletic do not negotiate when it comes to selling their top stars because they limit themselves to only signing Basque players, meaning the only way Chelsea could bring Kepa to Stamford Bridge was by activating his buyout clause.
Kepa made his international debut for Spain in November, keeping a clean sheet in a friendly win over Costa Rica, and was named to the Spain squad for the World Cup in Russia this summer, though he didn't play.
He will train with his new Chelsea teammates for the first time on Thursday and could even make his debut in the club's opening Premier League fixture against Huddersfield Town on Saturday.
He becomes the third acquisition of a chaotic summer transfer window for Chelsea, following the £50m capture of Jorginho from Napoli and the signing of third-choice goalkeeper Robert Green on a free transfer.