Manchester City captain Vincent Kompany will undergo a scan on Monday after being forced out of Saturday's 3-1 win against Everton with a groin injury, Goal understands.
The Belgium international limped off in the 34th minute at the Etihad Stadium, and although initial tests indicated an inflamed muscle there are now fears that he has suffered a strain, or worse, after he continued to feel pain on Sunday.
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The 27-year-old has been called up by Belgium to face Croatia and Wales on Friday and Tuesday, but faces a battle to be fit to play.
National team manager Marc Wilmots knows a draw or better in Friday's clash in Zagreb will guarantee their place at the 2014 World Cup in Brazil, and has risked the wrath of Aston Villa boss Paul Lambert by calling up first-choice striker Christian Benteke, who is recovering from a hip flexor injury.
Meanwhile, Martin Demichelis has stepped up his own recovery from a knee complaint.
The Argentine was brought in as defensive cover by City at the start of September, but picked up an injury almost immediately and was ruled out of action for six weeks.
The protective knee brace that was used to aid his recovery has now been removed, and the 32-year-old will now resume light training while his club team-mates are away on international duty before joining full sessions next week.