The status of South Africa's friendly match with Spain on Tuesday could be downgraded from an A international because the World Champions used more substitutes than they are permitted.
If Fifa changes the grade of the match it will not carry any world ranking points, meaning South Africa's 1-0 win is effectively worthless.
The Spanish made seven substitutions, one more than Fifa regulations allow.
Napoli keeper Pepe Reina was the final change, on for injured Victor Valdes.
That switch came in the 81st minute, despite Spain defender Alvaro Arbeloa putting on the goalkeeper's shirt in readiness to end the match between the posts in place of Valdes (pictured).
When Spain coach Vincent del Bosque overruled his player and sent on Reina, South Africa coach Gordon Igesund attempted to remonstrate with the Spanish bench but was ultimately ignored.
A Fifa spokesman told BBC Sport that the governing body is "in the process of gathering the official reports of the said game in order to analyse possible next steps".
Fifa's regulations state:
- In national "A" team matches, up to a maximum of six substitutes may be used.
- In all other matches, a greater number of substitutes may be used provided that the teams concerned reach agreement on a maximum number and the referee is informed before the match. If the referee is not informed, or if no agreement is reached before the match, no more than six substitutes are allowed.
The match was arranged for Spain to return to the scene of their 2010 World Cup triumph where they lifted their first world title.
But it was South Africa who came out on top thanks to a Bernard Parker strike in the 56th minute, giving them one of their biggest victories.