Chelsea will start the new season without goalkeeper Petr Cech after scans revealed a torn calf muscle, the Premier League champions said on Wednesday.
"Cech has torn a calf muscle in his right leg and is expected to be out for a month," Chelsea's website said. The season starts on August 14.
The 28-year-old, who sustained the injury during pre-season training on Tuesday, was also troubled with calf problems last season, missing a month during February and March after picking up an injury against Inter Milan in the Champions League.
Chelsea have Ross Turnbull, who deputised for Cech in the second leg of the Champions League defeat by Inter last season, and Portuguese Hilario as back-up keepers.