Romelu Lukaku was selected in the Belgium squad for the World Cup announced on Thursday despite coach Roberto Martinez admitting the Inter Milan striker was "medically unfit".
Lukaku has played just twice for Inter since the end of August because of a hamstring injury. He returned briefly in October but suffered a recurrence of the problem.
"Romelu is medically unfit, I think that's quite clear," Martinez said as he revealed his 26-man squad for Qatar.
"Romelu is at the moment receiving treatment and is entering that period that until the 22nd of November -- 24 hours before our first game -- he has the opportunity to get himself fully fit."
FIFA will allow teams to replace players unable to compete because of injury or Covid-19 up to 24 hours before their first match at the World Cup.
Lukaku is Belgium's all-time top scorer with 68 goals in 102 appearances.
The 29-year-old has endured a difficult past 18 months after he rejoined former side Chelsea at the start of last season in a club-record £97 million transfer.
After falling out of favour at Stamford Bridge, Lukaku returned to Inter on loan in the summer but has been limited to three starts in his second spell in Italy.
Martinez conceded last month there were also question marks over captain Eden Hazard, who has played a total of 229 minutes for Real Madrid this season.
"Nobody is trying to look away from the reality. Eden hasn't played consistently for a long, long time," Martinez told state broadcaster RTBF.
"Another question is can he play for 90 minutes? Can he play seven games in a short period of time?"
Kevin De Bruyne, Thibaut Courtois, Axel Witsel, Jan Vertonghen and Toby Alderweireld were all key parts of the team that finished third in Russia four years ago.
Belgium start their Group F campaign against Canada on November 23. They will also face Morocco and 2018 runners-up Croatia.
Goalkeepers: Thibaut Courtois (Real Madrid/ESP), Simon Mignolet (Club Brugge), Koen Casteels (Wolfsburg/GER)
Defenders: Toby Alderweireld (Royal Antwerp), Jan Vertonghen (Anderlecht), Zeno Debast (Anderlecht), Leander Dendoncker (Aston Villa/ENG), Wout Faes (Leicester City/ENG), Arthur Theate (Rennes/FRA)
Midfielders: Thomas Meunier (Borussia Dortmund/GER), Timothy Castagne (Leicester City/ENG), Thorgan Hazard (Borussia Dortmund/GER), Kevin De Bruyne (Manchester City), Axel Witsel (Atletico Madrid/ESP), Youri Tielemans (Leicester City/ENG), Amadou Onana (Everton/ENG), Hans Vanaken (Club Brugge), Yannick Carrasco (Atletico Madrid/ESP)
Forwards: Eden Hazard (Real Madrid/ESP), Leandro Trossard (Brighton/ENG), Romelu Lukaku (Inter Milan/ITA), Michy Batshuayi (Fenerbahce/TUR), Charles De Ketelaere (AC Milan/ITA), Lois Openda (Lens/FRA), Jeremy Doku (Rennes/FRA), Dries Mertens (Galatasaray/TUR)