The 26-year-old posted a screenshot of a $10,000 win on Melbourne Cup outsider Knight's Choice. Underneath was a blurred image of previous bets, with at least one of them on rugby league.
NRL players are forbidden to bet on games as outlined in their code of conduct, but Brimson's manager Jim Banaghan said his client had nothing to be concerned about.
"It is all going to die a very simple death because the account is his mother's and the reason she backed it is because her surname now is Knight," Banaghan told AAP.
"She put a fan's bet of $100 on it and that is the only bet she has had in the last seven months. The previous (bet) was on her son to score a try. It is all her account.
"I have got the message flows from her to him, the whole lot, and it is on her account."
Banaghan said Brimson had lost on his own bet but got a text from his mum that she had won, and that the screenshot that he posted was from her account.
The veteran player manager said Brimson had put the shot of the "win" up in a rush and was unaware of the bet underneath.
"It is just young men with social media," Banaghan said.
AAP has reached out to the Titans. The club has put out a statement on the matter.
"The Gold Coast Titans have referred a social media post made by AJ Brimson to the NRL's Integrity Unit," the club said."The club can't comment further on this matter at this time."
