Roberto Martinez revealed that Romelu Lukaku is an injury doubt for Belgium's World Cup blockbuster tie against England after the in-form striker picked up an ankle injury on Saturday.
Lukaku and Eden Hazard both netted twice as the Red Devils routed Tunisia 5-2 to leave them top of Group G and on the verge of the last 16.
But the Manchester United forward came off in the second half at the Spartak Stadium in Moscow.
"We need to look at Lukaku's ankle. He took a knock and has to be assessed," said Martinez, who revealed man-of-the-match Eden Hazard also picked up an injury.
"Eden Hazard has a calf knock, Dries Mertens has an ankle problem. There will be major changes against England.
"If we could have seven days to prepare, I'd say we'd start with the same team, but the reality is that you are only as good as the 23 players."
Lukaku's absence would be a blow to Belgium's hopes against England, with top spot in the group likely to be at stake.
The United player already has four goals at Russia 2018 to leave him as joint top scorer alongside Portugal's Cristiano Ronaldo.
However, there was some good news for Belgium boss Martinez, with Chelsea midfielder Hazard expected to be fit to face England in Kaliningrad on Thursday.
"I felt something in my calf in the first half but nothing big and I think I will be OK tomorrow," he said.