Police were called to the Ireland football team's hotel after Roy Keane was involved in a fight with a member of the public, say reports.
Medical help was provided by police officers who attended the Portmarnock Hotel and Golf Links, in Dublin.
It is understood Keane himself called the police and that no criminal complaint was made.
Keane's belligerent attitude has got him involved in several controversies over the years, including with team-mates at Manchester United and in public.
Keane was with the Ireland team ahead of Friday's Euro 2016 qualifying match against Scotland on Friday.
Football chiefs at the Football Association of Ireland (FAI) were backing him last night over the incident.
Team manager Martin O'Neill was told about what happened involving his deputy, a spokesman said.
The FAI said that reports Keane may have punched someone were "inaccurate." An eye-witness described what happened as "fairly innocuous."
"Following inaccurate media reports which refer to an incident involving a member of the public this evening at the Republic of Ireland team hotel, we wish to clarify that Roy Keane called the Gardai following the incident.
"The manager, Martin O'Neill and the FAI are fully aware of the circumstances surrounding this event, and the assistant manager has their full support."