Joao Felix has become the first casualty of the planned Chelsea clear-out under Mauricio Pochettino which could stretch into double figures.
Atletico Madrid president Enrique Cerezo confirmed Felix will return to his parent club after a six-month loan, a day after Pochettino's Chelsea appointment was confirmed.
Chelsea are prioritising reducing the size of their squad this summer which has swelled to more than 30 players after splurges in this season's two transfer windows.
The club hope that well over 10 players will go to help make the situation more manageable for Pochettino, who is due in England this week as he prepares for his new job.