The ankle injury sustained by new signing Romeo Lavia is a "sad situation", says Chelsea manager Mauricio Pochettino.
The 19-year-old limped out of training last week, prompting fears he could be out of action for a number of weeks.
He is yet to make an appearance for the club since his summer arrival from Southampton in a £58m deal.
"It's a sad situation because he was nearly ready to be involved," said Pochettino.
"Lavia was training well last week and in the international break he twisted his ankle so we are waiting for Monday to find out more.