Goal reported on Tuesday that a move was in the pipeline and it was completed formally on Thursday as part of the deal that saw Thibaut Courtois move in the opposite direction, hours before the transfer deadline in England.
Real Madrid midfielder Mateo Kovacic is refusing to train as he tries to force through a move to Stamford Bridge.
AC Milan have opened talks with Chelsea to sign the Frenchman on an initial loan deal with an option to make the move permanent on the basis of his performances at the San Siro. But the nail in the coffin was not even being on the bench during Chelsea's recent Community Shield loss to Manchester City.
Meanwhile, the BBC reports that West Ham are close to signing Arsenal forward Lucas Perez, who spent last season on loan at Deportivo La Coruna.
According to Sky in Italy, Bakayoko could join the Serie A outfit as the Blues are dealing with a packed midfield consisting of N'Golo Kante, Jorginho, Cesc Fabregas, Ross Barkley, Ruben Loftus-Cheek and Danny Drinkwater.
With Milan leading the race for Bakayoko, Everton's interest appears to be dependent on whether or not they land Zouma.
Bakayoko's initial presence in Chelsea sides during pre-season sort of felt like Sarri would use him well this season, but their pursuit of Kovacic has now made him surplus to requirements.
The key question for Mourinho is whether he can finally get the best out of Alexis Sanchez, Paul Pogba and Romelu Lukaku and find a positive style of play that the Old Trafford faithful demand.
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