Diafra Sakho faces a lengthy ban after Senegal football chiefs made a formal complaint to FIFA.
West Ham striker Sakho was absent from his homeland's short-lived Africa Cup of Nations campaign, which ended on Tuesday with a group-stage exit, after suffering a back injury.
But Senegalese FA chiefs were furious that he was fit enough to play - and score the winner - in Sunday's FA Cup tie at Bristol City.
They have contacted world football's governing body FIFA demanding action - and that could see him suspended from playing for West Ham at Liverpool on Saturday and in further games.
Although Senegal are out, FIFA have the power to stop Sakho appearing for his club for the duration of the tournament in Equatorial Guinea - which ends on February 8 - but they could impose an even longer ban and a heavy fine.
Senegal fans are even demanding Sam Allardyce's men are kicked out of the FA Cup, where they are scheduled to face West Brom in the last 16.
A FIFA spokesman told Mirror Sport on Tuesday night: "We can confirm that we have been contacted by the Senegal FA concerning this matter. The matter is now pending with our services. We cannot comment further at this stage."
FIFA will investigate and pass on their findings to the Football Association, who are aware of the complaint.
West Ham stressed on Tuesday that they had not broken any rules, and they are adamant that Sakho will be picked for this weekend's trip to Liverpool.
While the rest of the team flew to Bristol, Hammers' top-scorer Sakho was driven there in a luxury Mercedes saloon car to protect his back. He will make a 450-mile road trip to Liverpool by the same method.
West Ham supplied a medical report - carried out by an independent specialist - which stated Sakho would be unable to fly for six weeks. Senegal were therefore unable to select him in their 23-man squad for the finals.
But, three weeks later, he is playing in matches, and that has enraged his countrymen.
West Ham stressed that the independent specialist cleared him to play at Ashton Gate on Sunday, but insisted he could not fly to Bristol because it would make the back injury worse.
The Londoners told Mirror Sport they invited Senegal to perform their own medical inspection but, to the best of their knowledge, they did not do so.
They also say they have been inconvenienced, because Sakho has missed four games with the injury he originally suffered while on international duty.
Senegal FA general secretary Victor Cisse was contacted by Mirror Sport on Tuesday, and the organisation is considering its next step.
Sakho tweeted his anger over the row on Monday after an anti-West Ham campaign was launched on social media in Senegal.
Senegal's head coach Alain Giresse said after Sakho's FA Cup winner on Sunday it "set a dangerous precedent" that West Ham could claim he couldn't fly to matches but could take part in them.
Giresse added: "When you cannot fly for six weeks and then suddenly you're playing a football game, there must be miraculous medicine in England."