The 29-year-old has played just four games in Serie A this season after picking up a thigh injury at the end of August.
Globo reported that Lukaku will definitely miss the first two games of the tournament against Canada and Morocco, and may struggle to recover in time for Belgium’s final group game against Croatia.
His absence will be keenly felt by the Belgium national team led by Coach Roberto Martinez, as he is the European country’s record scorer with 68 international goals and their most senior striker by a distance.
Lukaku did not join in Belgium’s first proper training session since they arrived in Qatar on Friday as he continues his recovery from a hamstring injury.
Even in Lukaku’s absence, Belgium boasts an exciting array of attacking talent in their squad. The likes of Kevin De Bruyne, Eden Hazard, and Dries Mertens will provide a stern test for opposition defences.
Many of Belgium’s top players are now over 30, though, and there is a concern that this World Cup will be the last chance for this group of players to win an international trophy.