Ben Chilwell was seen telling Chelsea team-mate Mason Mount that his hamstring "popped" as he was dealt a cruel injury blow on Wednesday night.
The Blues left-back went down in the final minutes of Wednesday's win over Dinamo Zagreb and had to be helped off the pitch. He later left Stamford Bridge on crutches which has cast major doubt over his World Cup hopes with England.
The tournament in Qatar is just weeks away with the Three Lions beginning their campaign against Iran on November 21. Chelsea boss Graham Potter was not optimistic about his left-back's situation after the win in west London, admitting it is a "concern".
He said: "It’s not great. Obviously when he pulls up like that it’s a concern, so we need to scan it, but it’s not positive at the moment. It’s a blow for us on an otherwise positive evening, I think. It’s a blow, to see him pull up like that is not a great sight.
"So fingers crossed that when we get it scanned it isn’t as bad, as it can be not severe. We have our fingers crossed at the moment, but obviously we’re disappointed.
"I think you’d have to say there are worries about him being okay for the World Cup. I don’t want to add any more than that, but obviously when a player pulls up like he did and he felt it, it’s never positive. He just felt something as he was setting off and it’s not nice."
Would Chilwell have started for England at the World Cup? Tell us what you think here.
Chilwell was set to be among the leading candidates to play on the left of England's defence. At Euro 2020 last summer the Chelsea star wasn't handed a single minute with Luke Shaw and Kieran Trippier both preferred by Southgate.
This time round though Chilwell was poised to enjoy more involvement due to Shaw's drop in form and Trippier's need to play on the right due to the amount of injury concerns in that area. The midseason World Cup has seen injuries play a far greater role than usual, which has been a source of criticism.
England are already sweating on the fitness of several key individuals. Manchester City's Kyle Walker and Chilwell's colleague Reece James are both aiming to get back before the tournament. The two individuals can cover right-back as well as centre-half and would both have been fancied to start.
Chelsea's N'Golo Kante has already seen his World Cup hopes ended as he deals with a hamstring injury. The Blues midfielder helped France lift the trophy in Russia four years ago but will be a major absentee in the Middle East.
