Chilwell pulled up with an apparent hamstring problem in Chelsea's 2-1 win over Dinamo Zagreb in the Champions League on Wednesday night and left the stadium on crutches.

England's first World Cup match is against Iran on November 21 and manager Gareth Southgate has a deadline of November 14 to name his 26-man squad, leaving Chilwell in a precarious position.

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Asked if the tournament in Qatar was now a concern for Chilwell, Chelsea boss Potter said: "I think you'd have to say so.

"Obviously I don't want to say any more than that but when a player pulls up like he did, and he felt it, so it's never positive.

"It's a blow for us, on an otherwise positive evening. To see him pull up like that is not a great sight, fingers crossed when we get it scanned it won't be as severe, but fingers crossed on that at the moment.

"[It's] not great. Obviously when he pulls up like that it's a concern so we need to scan, but it doesn't look 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, it's not a great sight.

"So fingers crossed when we get the scan it isn't bad, it can be not severe, but we have to have fingers crossed at the moment. But clearly we're disappointed."

Chilwell appeared to pull his hamstring chasing a ball in stoppage time and though he got to his feet and played the final seconds of the match.

The England defender, who has had so much bad luck with injuries in the past, had to be carried across to the tunnel at the full-time whistle.

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"He didn't play at the weekend," added Potter, "there was a thought that he could play tonight and have enough time to recover for the weekend.

"So we've tried to manage him, he's never played the three games in a week, he's had to have the build up, it's been good for him.

"That's what makes it very frustrating. It's a blow for us and a blow for him and sadly he won't be the only one who's affected like that in this period because October was incredibly challenging, the games that we had to play, but it is what it is."

Pulisic: We hope it's not as bad as we think

Chelsea team-mate Christian Pulisic is hoping the injury to Chilwell is "not as bad as we think".

"You never like to see anyone go down with injuries," he told Sky Sports News. "For Chilly, we are hoping that it's a quick one and hoping that it's not as bad as we think.

"I know he will be back soon. We want everyone to be healthy and have an opportunity [to go to the World Cup]."

Conor Gallagher, who is also an international team-mate of Chilwell, spoke to the left-back after the game and said he was "disappointed" to have picked up the injury.

"We are really hoping that it's not too bad," Gallagher told Sky Sports News.

"Everyone is very hopeful, he seems alright. He's not sure quite how bad it is.

"I guess he is going to get a scan on it in the next couple of days, so we will just have to wait and see."

Chelsea fixtures before World Cup

Chelsea vs Arsenal, Premier League - Sunday November 6; kick-off 12pm

Man City vs Chelsea, Carabao Cup - Wednesday November 9; kick-off 8pm, live on Sky Sports

Newcastle vs Chelsea, Premier League - Saturday November 12; kick-off 5.30pm - live on Sky Sports

England World Cup fixtures

England vs Iran - Monday November 21; kick-off 1pm

England vs USA - Friday November 25 ; kick-off 7pm

Wales vs England - Tuesday November 29; kick-off 7pm