Eden Hazard was excused from Chelsea's Europa League trip to PAOK after twice telling Maurizio Sarri he was tired.
The 27-year-old playmaker led Belgium to third place at the World Cup and has been in scintillating form for the Blues.
Hazard scored a hat-trick last Saturday against Cardiff as Chelsea claimed a fifth Premier League win from five games before asking to be omitted from the trip to Greece.
Sarri said in Thessaloniki on Wednesday: "He told me after the national team (duty earlier this month) and the match against Cardiff he was a little bit tired, so I thought it was better to stay at Cobham, to have training and rest."
Hazard received special dispensation to delay his return from his post-World Cup break until after the Community Shield on August 5.
He made substitute appearances in the first two Premier League games and has scored five goals in his subsequent three starts, delighting the Blues faithful who feared he would make a summer switch to Real Madrid which never materialised.
Brazil defender David Luiz has also been rested, having returned to become an integral member of the squad under Sarri. Luiz fell out of favour under Sarri's predecessor, Antonio Conte.
Luiz's compatriot Willian cut a frustrated figure under Conte, who was sacked after a fifth-placed league finish saw the Blues drop into the Europa League.
Willian was linked with summer moves to Manchester United and Barcelona and previously said he would have left Stamford Bridge had Conte stayed.
"I don't want to talk about the past," Willian said.
"At the moment I'm happy, with a new manager, with a new profile of football. We have a great team atmosphere, we have great players. We can do everything this season to win titles.
"I am very proud to stay and be a Chelsea player. It's an honour to play for this club. I am very happy at Chelsea.
"Everyone knows what happened in the last window, but my mind was always at Chelsea.
PA
