Chelsea captain John Terry had to be replaced because of injury in his side’s final match before their first Premier League game of the season.
Terry, who signed a new one-year deal in May, limped off after a collision during yesterday’s 4-2 win over Werder Bremen in Germany.
The 35-year-old was immediately replaced by manager Antonio Conte after being caught in the head.
Chelsea starts the new season at home to West Ham United on August 15.
Eden Hazard and Oscar gave Chelsea a 2-0 lead against Werder Bremen before Claudio Pizarro pulled a goal back.
Diego Costa made it 3-1 before half-time only for Lennart Thy to reduce the deficit. Pedro added a fourth in the closing stages.