Chelsea defender Ben Chilwell has suffered a "bad" hamstring injury with no timescale yet put on his return, says Blues boss Mauricio Pochettino.
Chilwell has had a scan on the injury that forced him off late on against Brighton in the EFL Cup on Wednesday.
Chelsea are already without Reece James until after the international break with a thigh problem.
"When they're at their best, they are the best full-backs in the world," said Pochettino.
"At all clubs, important players are missed when they don't play.
"If the question is 'do we miss them?