The incident took place outside a bar in the early hours of Wednesday morning in Brussels, the 21-year-old’s home city.
As two men fought on the ground, Denayer aimed a single kick at one of them before others jumped in.
The defender, who was on loan at Sunderland from Manchester City this past season, admitted his part in the fracas, but insists he was only acting to protect his friend.
“I was on my way to my car when I heard a friend shouting,” he told the Belgian media. “I saw that my friend was in danger and had to intervene.
“I responded instinctively. My sole purpose was to protect my friend.”
Denayer’s agent, Desse de Preter, added: “It can be perceived as aggressive, but it is clearly a defensive response from Jason. His reaction was one of panic and protection.
“Jason spent two days this weekend in Belgium because he had been given leave from his club.
“He decided to go out for a night with his best friends, but when he left the nightclub it went wrong.
“Jason stepped calmly to his car, which is down the street when he heard a sudden noise behind him.
“When he turned he saw his best friend had become involved in a skirmish. Jason called to stop but without effect.
“It is true that he has handed out a kick, but it was intended only defensive.”
Denayer won the PFA Scotland Young Player of the Year award in his single season with Celtic after joining on loan for the 2014/15 campaign.