England prop Kyle Sinckler has been cited for an alleged eye-gouging incident in Harlequins' Aviva Premiership defeat at Northampton on Saturday.
Sinckler was accused of the offence by Michael Paterson following an incident that took place in the 49th minute, but referee Luke Pearce decided replay footage was inconclusive and awarded a penalty only for removing the Saints lock's scrum cap.
The entry-level sanction for making contact with the eye and/or eye area is a 12-week suspension, threatening the combustible British & Irish Lions tighthead's involvement in England's autumn series against Argentina, Australia and Samoa.
Sinckler must appear before a Rugby Football Union disciplinary panel in Bristol on Tuesday evening.
Paterson claimed immediately that he had been gouged while trapped at the bottom of the breakdown and when asked by Pearce to confirm his accusation, the New Zealand-born forward replied "100 percent".
The four available camera angles were examined on the big screen at Franklin's Gardens but each was inconclusive except to show Paterson's headgear being pulled off, resulting in a penalty.
Sinckler, who was arrested by Auckland police for a minor offence after the final Lions Test against New Zealand in July, denied any wrongdoing and was supported by his director of rugby John Kingston.
"Unequivocally, it was not a gouge. Absolutely not," Harlequins boss Kingston said.
"Kyle said he made contact with Paterson's head gear. He can't do that. There was a purge on it a couple of years ago because it's the sort of thing that cheeses people off, so leave headgear alone."
Kingston then rounded on Northampton by drawing attention to the extensive bruising around the left eye of Dave Ward, suggesting the injury was a result of foul play, although no Saints player has been cited.
"I have to say...my hooker has got a rather nasty eye and I know how it happened because he's told me -- and I believe him," Kingston said.
"I'm pretty disappointed about that and he's not happy about it."
Sinckler, England's second choice tighthead for the autumn campaign that starts against Argentina on November 11, had been treading a fine line until his fracas with Paterson as his aggression threatened to boil over on several occasions.
The 24-year-old was warned over his conduct by Eddie Jones after the Lions tour and was omitted from the most recent training squad named by England's head coach.
"Kyle Sinckler of Harlequins has been cited by independent citing commissioner Chris Catling and is to appear before an RFU disciplinary panel charged with allegedly making contact with the eye and/or eye area of Northampton Saints' Michael Paterson, contrary to law 10.4(m)," read a Rugby Football Union statement.
Quins lock George Merrick has received a citing commissioner's warning -- the equivalent of an off-field yellow card -- from the same match after charging into a ruck illegally during the closing stages.