"I am really happy and excited to be here at Chelsea", Kovacic said in a statement.
"I want to thank Athletic for the love and respect they have instilled in me during these years and I'll always take that with me".
"I saw him one year ago [when I was at] Naples and my first impression was he was a very good goalkeeper".More news: Google Pixel 3 XL live pictures and unboxing video emerge
"I would say that I am a calm, settled goalkeeper".
"The Spanish global goalkeeper arrives ahead of the new Premier League season, having signed a seven-year contract at Stamford Bridge", Chelsea said in a statement.
Arrizabalaga, who made his full worldwide debut for Spain against Costa Rica in a November friendly a year ago, will feel he has plenty to prove at Chelsea, as he attempts to live up to his remarkable price tag.
"I have spoken to various players before I came here; [Cesar] Azpilicueta, [Alvaro] Morata, Pedro".More news: Younes Bendjima's sexy cuddle buddy breaks her silence
He has spent the past two seasons in Bilbao's first team, making 53 La Liga appearances, and has one worldwide cap.
Kepa is eligible to make his debut for Chelsea in the Premier League opener against Huddersfield Town on Saturday and said: "It's a very important decision for me, for my career, and also for my personal life".
"What attracted me to Chelsea?".
As displayed by Manchester City's Ederson, whose previous world record fee now looks like a bargain, a keeper that can be composed under pressure and deliver smart passes is a huge advantage to have in the Premier League.More news: Fallout 76 to be exclusive to Bethesda.net