Omeruo had been training with the squad at the Cobham training grounds but has not been included in the travelling squad as he is expected to join Turkish champions Besiktas over the next few days.
A source close to the player told Turkish-Football that Besiktas have struck a deal with Chelsea to sign Omeruo on a season-long loan deal.
The Istanbul giants have agreed a release clause in the contract and will have the option to sign the 22-year-old on a permanent basis.
The Istanbul giants are expected to cover his €1.1 million salary over the course of next season.
Omeruo did of course spend last season out on loan for Super Lig outfit Kasimpasa so he is familiar with the country.
Travelling Chelsea squad in full: