Chelsea fear Callum Hudson-Odoi faces a lengthy spell on the sidelines with an achilles injury.
The Blues youngster limped off five minutes before half-time of the 2-2 draw with Burnley at Stamford Bridge on Monday night.
He will be assessed over the next 24 hours but the early signs are not good, according to assistant boss Gianfranco Zola.
A significant injury would be a real blow for Hudson-Odoi, who recently broke into the Chelsea first team in the Premier League and is hugely popular among fans.
“It’s not an easy one. I think it’s a serious injury. It’s on his achilles tendon,” Zola told reporters after the game.
“I cannot tell you the full extent of it. I haven’t been told if it’s ruptured. I think he will have to have an examination. But it’s not looking good.”
N’Golo Kante also had to go off – the midfielder was withdrawn at half-time – but Chelsea do not believe the Frenchman’s injury is a cause for alarm.
Zola explained: “He went down and as he went down he fell on the foot of a player, so he just had an intrusion in his ribs and he couldn’t breathe properly and that’s why he came off. He will be alright. It’s not anything serious.”