FIFA has confirmed that it is investigating an incident involving Robbie Brady and Ashley Williams which took place during the Republic of Ireland's 1-0 win over Wales on Monday night.
Television cameras captured Ireland midfielder Brady apparently flicking his head in the direction of the Welsh defender's back in the 61st minute of the World Cup qualifier in Cardiff.
If charged, the 25-year-old Burnley player could be a doubt for the two-legged playoffs, which will be played in the first fortnight of November.
"We are gathering evidence and cannot comment further," a FIFA spokesperson told BBC Sport when asked about the incident.
Brady has already served two suspensions during the Republic's Group D campaign, having collected four bookings.