The Belgian winger has found himself axed from Chelsea’s Champions League squad for Tuesday’s game against Steaua Bucharest, and has been forced to train with the under-21’s.
De Bruyne is now facing a testing few months at Stamford Bridge, and will look to seek either a loan or permanent move in January in order to save his World Cup dream.
Mourinho had previously promised the 22-year-old he would play a part for the first team this season, and blocked a return loan move to Werder Bremen.
Champions League finalists Borussia Dortmund were also denied the opportunity to take De Bruyne on loan in the summer, and may return with another offer in January.
De Bruyne started the first game of the season against Hull City, but has since struggled to make the first team.
He was left out of the 18-man-squad for the trip to Tottenham at the weekend, and Mourinho has angrily explained the reasoning.
Mourinho walked out of his Champions League press conference after growing frustrated with questions about the Belgian, however he did reveal he was not in the squad due to his poor form.
“He’s not selected because I didn’t like the match he played against Swindon and I didn’t like the way he was training,” Mourinho said.
“But you have this tendency to only ask about the guys that are not selected. See you Tuesday.”