It was the 23-year-old's first game since his return from the knee injury that ruled him out of England's World Cup squad.

"It's the same area, so we are concerned," Potter said.

"It's really too soon [to tell]. We'll have to see over the next 24-48 hours. He felt something there and we will have to find out the extent of it and keep our fingers crossed.

"He's been really disappointed to miss the World Cup, of course. It was a huge blow to him. You could see today his quality and what he brings to the team. He is a world-class player. You see it from the outside but not until you work with him do you see how good he is.

"He could play in any team in the world, and any team would miss him. The plan was to play 60 minutes today so now he's disappointed, of course.

"We hope it's not as bad as it was and he can have a speedy recovery."

is substitution, James had been one of the outstanding performers in a rejuvenated Chelsea side, who had not won in five league matches before the season was paused for the World Cup.

"It's a step forward for us as a team," Potter added.

"Credit to the players. You're never sure how it'll go with the break we had. The first-half performance was good. The attitude was fantastic. It was a deserved win.

"We weren't in the best of moments, so you have to use breaks as best you can and we did that to evaluate and reassess and get injured players back. We used it as best we could, even with players coming back at different times, and the attitude of the players has been fantastic."

Kai Havertz also impressed for Chelsea, as he brushed off a disappointing World Cup campaign with Germany - who went out in the group stage - to score the opening goal for the Blues, created by Raheem Sterling.

"I know the vision Raheem has. He loves to play these balls," the German forward told Prime Video.

"It was a perfect ball and I was happy to score. The win and the goals hopefully will give us some confidence.

"He [Graham Potter] gives me the freedom to do whatever I feel comfortable on the pitch. I like to play free and to be in the box. He gives me a lot of confidence."