Chelsea are waiting to discover the extent of the injury suffered by Carney Chukwuemeka at West Ham.
The 19-year-old scored his first goal for the Blues at the London Stadium to cancel out Nayef Aguerd’s early header.
But Chukwuemeka had to be helped from the field with a knee injury shortly before half-time.
Reaction from Mauricio Pochettino following yesterday.
— Chelsea FC (@ChelseaFC)
“We need to assess him (on Monday),” said Blues boss Mauricio Pochettino.
“There will be an assessment with the doctor. We hope it’s not a big issue, but we need to wait.”
Further goals from Michail Antonio and Lucas Paqueta’s stoppage-time penalty condemned Chelsea to a 3-1 defeat, despite West Ham playing the last 25 minutes with 10 players following Aguerd’s red card.
The Blues had the chance to go 2-1 ahead before half-time but Enzo Fernandez’s spot-kick was saved by Alphonse Areola.
France international Areola insisted he was confident about saving the penalty despite his wretched record.
The 30-year-old is West Ham’s new first-choice this season having been promoted ahead of veteran Lukasz Fabianski, who has an excellent record of saving spot-kicks.
Areola, by contrast, had let in all four of the penalties he has faced for West Ham, as well as watching all 10 fly past him in a Carabao Cup shoot-out defeat by Blackburn last season.
He said: “I think we showed that we are strong defensively and can score after that.
“We tried to survive first and then with the red card, which was unlucky, we showed that we have the character and we are now experienced.
“I was quite confident on the penalty. I was ready and luckily for me and for the team I stopped it. I was happy and happy for the team, and I think it helped the team to push and keep our belief.”