Ex-Wales and Newcastle soccer player Malcolm Allen has been bailed after admitting kicking a girl in the head.
Allen told the court he thought his sister was being attacked
Allen, 39, from Deiniolen, Gwynedd, told Caernarfon Crown Court he went "over the top" when he thought his sister was being attacked in Bangor.
The BBC commentator admitted affray but denied common assault. The charge was ordered to lie on file.
Judge John Rogers said Allen's "sensible" guilty plea would make a "huge difference" to sentence.
Allen, who also played for Norwich and Watford before injury cut short his career, admitted the offence outside a chip shop in November 2005.
Nicholas Williams, defending, said the incident in the town's High Street happened after Allen had a phone call from his sister's disabled partner, who claimed his sister was being attacked by a group of girls.
Mr Williams said the defendant arrived at the scene to find his sister "on the floor with a female".
Mr Williams said: "He then did what he did solely with the intention of defending his sister.
"But he accepts in doing so he went over the top and would have to accept during that he did kick a girl to the head."
The prosecution accepted there was an incident in a chip shop.