The Mirror says in an interview titled 'My Footballing Firsts" on 'The Fifth Stand' app, it was revealed that Kovacic had completed his move from the Spanish club.
The post began: "After securing a permanent switch to Stamford Bridge following a successful loan spell at Chelsea from Real Madrid, we caught up with Mateo Kovacic..." before detailing the rest of the interview.
It even contained quotes from Kovacic on the transfer, who said: "It was an amazing feeling to sign for Chelsea, first on loan and now permanently.
"It is a fantastic club, with great team-mates and we play a good style of football.
"I am very happy to be staying here and very proud to be a Chelsea player."
Recent speculation suggested that Chelsea were set to finalise a deal worth £45 million for Kovacic to stay at the club after a successful loan spell last season.