Belgium could be without both of their first-choice centre-backs, captain Vincent Kompany and Thomas Vermaelen, for their FIFA World Cup™ Round of 16 clash with USA.

Coach Marc Wilmots said Vermaelen, who has a knee problem, would definitely miss the game while Kompany is also an uncertain starter as he struggles to overcome a groin injury.

However, Wilmots, who is yet to lose a competitive match since he took over the Red Devils in 2012, reassured that there were no such concerns over attacking midfielder Marouane Fellaini, who quit training on Sunday with an ice pack on his left calf.

"I don't know about Vincent and whether he will be fit," said the 45-year-old. "We will see how it evolves.

"Thomas, though, has not enough time to be fit by tomorrow. He will be fit if we make the quarter-finals. He will return to full squad training in a day or two. Marouane is fine, no problem."

The absence of 30-year-old Kompany, in particular, would be a huge blow for a Belgian side that won all three matches in their group but without really convincing performances.