Retired NRL great Brad Fittler says Sandor Earl must be handed a harsh penalty as a lesson to other players about the dangers of taking prohibited substances.

Earl was handed an infraction notice by the NRL after admitting to the use and trafficking of prohibited substances, including the peptide CJC-1295.

He faces a ban of four years to life for the offences, but it is believed his willingness to co-operate with ASADA's investigation may see his sentence reduced.

Speaking on SportsFan's Clubhouse on Thursday evening, Fittler said the only way to educate young players is to make an example of Earl.

"You can only educate them by [threatening] penalties," he told the gang.

"If you take this you'll be out for four years, it's as simple as that. It's too hard the other way.

Read the rest of Brad Fittler's thoughts here.