The Atlas Lions' doctor said on Thursday that Noussair Mazraoui and Achraf Hakimi, who were injured in Morocco's opening 0-0 draw with Croatia on Wednesday, were still doubtful for Sunday's game against Belgium.
The 24-year-old Bayern Munich defender "injured himself on the left side," said Abderazzak El Hifti. "We have examined him, but it is impossible to say if he will be able to participate in the next match or not," he added, assuring that new medical examinations are planned in the next two days.
The Paris SG international suffered a "slight injury" in the match against Croatia. The 24-year-old full-back "felt a pain in his leg at the start of the match, but continued to play despite this. We will be careful and do further tests to decide if he is fit to play on Sunday," he added.
Morocco, who play in Group F, held off the world runners-up 0-0 on Wednesday and are due to face Belgium on Sunday and Canada on December 1.
Noussair Mazraoui was injured in the 51st minute when he fell to the ground as he tried to pick up the ball after a shot by Croatia goalkeeper Dominik Livakovic. He lay on the ground for a minute before being replaced by striker Abderrazak Hamedallah. Achraf Hakimi was able to play until the end of the match.
The rest of Walid Regragui's men are fit for selection, buoyed by their performance against Croatia and ready for the Belgian challenge.
Kevin De Bruyne and his teammates have not lived up to the hype of being the second-highest ranked team, despite a 1-0 win over Canada on Wednesday.
Regragui, who took over as Morocco coach only three months ago, has restored unity to the 'Atlas Lions' ranks by bringing back Hakim Ziyech and Noussair Mazraoui.
The outgoing coach, Vahid Halilhodzic, had sidelined both players, much to the dismay of the Moroccan people.
The Moroccans are hoping to do as well in Qatar as their predecessors did in 1986 when the team became the first African team in history to reach the last eight of the World Cup.