Ben Chilwell will be out for three months with hamstring injury.
The England international pulled his hamstring on his left foot in Chelsea’s 2-1 over Dinamo Zagreb.
He underwent a scan on Friday and the injury was worse than feared, with the Chelsea defender set to miss the World Cup later this month.
Luke Shaw is now the only natural choice left-back for Gareth Southgate and will have to find a back-up option in a few days.
‘Following the injury sustained in our recent game against Dinamo Zagreb, Ben has undergone a scan on his hamstring,’ read a statement from Chelsea’s website.
‘Results show that Ben has suffered a significant injury and the defender is unfortunately expected to miss the World Cup.
‘Ben will now begin a rehabilitation programme with the club’s medical department.’
The 25-year-old missed majority of the prior season with an ACL injury and worked tirelessly to get back his place in Gareth Southgate’s squad.
‘Following my ACL injury I worked so hard to make sure I was ready for the World Cup,’ wrote the defender on Instagram.
‘It has always been a dream of mine. Unfortunately, this won’t be possible following my scan results.
‘It’s very difficult to take at the moment but I believe everything happens for a reason.
‘I will do all I can to get back playing for Chelsea as soon as possible. Thank you for the messages of support.’