The NRL will only investigate allegations of spitting that sparked a post-game fracas in the Wests Tigers-Manly Sea Eagles game if an official complaint is raised.
Manly rookie Samuela Fainu is reported to have spat at Tigers playmaker Brandon Wakeham late in Sunday's 22-16 Sea Eagles win.
The incident led to a melee at the time and a heated post-match exchange between Wakeham and Manly prop Josh Aloiai in the tunnel at Campbelltown Stadium.
NRL head of football Graham Annesley said because Wakeham opted against registering a complaint with referee Todd Smith, the match review committee had not explored the incident in forensic detail.
"There is nothing that they (the Tigers) raised issue with," Annesley said.
"There was no on-field complaint that was willing to be lodged by any particular player.
"So without evidence, they (the MRC) can't proceed, they can only proceed if they have some sort of video evidence or it can be an on-field complaint.
"But without either of those elements, there's not much I can do about that."