never knew there was anything wrong with him but just found this from an article online...

Chelsea have been dealt a huge blow in the title race with goalkeeper Petr Cech sidelined by a groin injury.
Reserve stopper Ross Turnbull stepped in for Cech at half-time during Chelsea's 2-1 victory over Everton at Goodison Park on Saturday.
The Blues are currently unsure how long Cech will be kept out for, with further tests needed to determine the recovery period.