The NRL's integrity unit is expected to call Andrew Fifita in for questioning over an alleged public show of support for one-punch killer Kieran Loveridge.
Fifita has been spotted displaying the initials FKL on his wristband in at least seven matches this year, according to News Corp Australia images.
The revelations come after the Sharks prop was warned by NSW Police on Wednesday for consorting with criminals after he made several visits to Loveridge in Cessnock jail.
Loveridge was responsible for the high-profile manslaughter of 18-year-old Thomas Kelly in 2012 during a night out in Kings Cross, and is serving a minimum 10-year sentence.
It's believed Fifita could have once coached Kelly's killer, and that FKL stands for either "For Kieran Loveridge" or "Free Kieran Loveridge".
However, an NRL spokesman said that if the claims were true, Fifita could run into trouble with the game's administration.
"If that is the case, it's inappropriate to use any football clothing or accessories to promote an association with criminal activity," an NRL spokesman said.
Fifita is believed to have attracted the interest of police for the warning after his name came up while they looked into the Lone Wolf bikie gang, which Loveridge is alleged to have links to.
Cronulla chief executive Lyall Gorman has also refused to comment on the matter until he investigates further.
On Thursday, before the alleged links with Loveridge were revealed, Cronulla coach Shane Flanagan said he had spoken to Fifita about the matter.
"Andrew hasn't been charged with anything, he's been warned for associating with these people,and he told me, 'you didn't grow up in the western suburbs'.
"A lot of his mates are in jail. That's the way it is. He won't desert them, but he understands he can't contact them."
Fifita attracted attention last year after he posted images on social media of former Wests Tigers prop Matt Lodge after he was arrested in in New York after he allegedly told two women: "This is the night you die".
Fifita was also suspended for six matches and fined $30,000 last year over his abuse of a referee at a junior rugby league match.