Asked if he would hesitate to ban anyone for life, Greenberg said: "There are massive penalties in place for players that do the wrong thing and the integrity of the game is central to that.
"If and when we need to make some hard decisions, we'll make them."
Strike Force Nuralda is the same Organised Crime squad task force looking into match-fixing allegations.
Fairfax Media reported Simona allegedly organised for bets to be placed through associates.
It's alleged the bets were minor but placed on players, who Simona was marking, to score tries.
Simona, who has played 79 games for the Tigers since making his debut in 2011, has been stood down from training and playing commitments while he is being investigated.
The NRL issued him with a notice of intention to cancel his registration and is facing being rubbed out of the game.
Under the NRL's betting code: "No NRL employee, NRL club employee, player, player manager or game official is allowed to participate, or be directly or indirectly involved in any way, in gambling in relation to rugby league. Or be involved directly or indirectly, in the provision of information not already in the public domain that might assist another person to gamble in relation to rugby league."
Greenberg defended the NRL's close ties to betting agencies and the prolific advertisement of odds during matches.
The NRL boss said players were well aware they couldn't bet on matches and the affair had nothing to do with gambling advertising.
"Players are acutely aware of their responsibilities, they know they can't bet on rugby league," Greenberg said.
"And if they do and are found guilty, there will be significant ramifications including career-defining decisions.
"Players put at great jeopardy their careers if they consider that.
"It's well-understood, it's contractual, there's enough education, every player knows the rules."
- AAP
