Donegal have made claims one of their players was on the receiving end of an alleged bite during Sunday's Division 1 football league match against Dublin in Ballybofey.
McBrearty is understood to have a significant graze consistent with teeth marks on his shoulder which he had checked out in Letterkenny Hospital on Sunday night.
Referee Padraig Hughes was notified of the allegation at half-time by Donegal officials and it has been mentioned in his report on the match. But once he or any of his officials didn't see the alleged incident happening, building a case will be difficult.
Hughes himself was in the wars when he twisted ankle ligaments early in the second half and had to be stretchered off and replaced by Michael Duffy in the 45th minute.
It is also believed that Dublin were made aware of the allegation after the match through contact between the medical staff of both teams.
Donegal secretary Hugh Martin Ferry has confirmed to the Irish Independent that a member of the Dublin medical staff visited the Donegal dressing-room afterwards to examine the graze.
Donegal are angered by the alleged incident but apart from confirming that the referee was informed, they do not want to make an issue of it and were happy to leave it with the referee.
They are understood to have taken pictures of McBrearty's shoulder to support the claims made to Hughes at half-time if required for any investigation. It will be up to the Central Competitions Controls Committee, who met yesterday, to initiate any investigation.
Donegal manager Jim McGuinness was not as calm as he normally is after games and was clearly perturbed by a number of matters during the game.
"A lot of stuff went on there that didn't add up," he admitted, a possible reference to the decision not to give Rory Kavanagh a penalty or possibly this alleged biting incident.
McBrearty is the star of the Donegal U-21 team who play Cavan in tomorrow night's Ulster final in Enniskillen. His participation is not thought to be in doubt because of the cut to his shoulder.
Dublin chairman Andy Kettle said last night that there had been no contact between the Donegal and Dublin County Boards on this matter.