Paul Vaughan's behaviour has been slammed as selfish by St George Illawarra coach Paul McGregor after their NRL loss to Sydney Roosters on Thursday night.
McGregor said he was disappointed in Vaughan's decision to break the NRL bubble to get breakfast earlier in the day - a move that has resulted in the prop being quarantined for two weeks.
After missing Thursday's 24-16 loss to the NRL premiers, Vaughan will also miss next week's clash with Parramatta.
Coming from a senior player and club leader, the news was tough to swallow.
"That's very disappointing," McGregor said.
"We're well aware of what our responsibilities are.
"We talk about it consistently so there's no reason for it except it's selfish behaviour."
Earlier on Thursday, Vaughan conceded there was no excuse for his actions and apologised to McGregor and teammates in a WhatsApp message hours before they took the field.
The State of Origin forward was caught having breakfast at a Wollongong cafe on Thursday morning, in a direct breach of the NRL's biosecurity protocols.
The news was a massive blow for the Dragons, who are facing must-win games without their best front-rower.
"I am very remorseful for the reckless and selfish decision I have made," Vaughan said.
"Everyone within the Dragons' bubble, including myself, are well aware of the protocols in place.
"I'm sorry for the harm my actions have caused to the club and my teammates."
Vaughan has been tested for COVID-19 and will require to pass another test before rejoining his teammates after his isolation period.
Vaughan's breach came on the same day South Sydney coach Wayne Bennett admitted he had lunch at a Sydney restaurant on Wednesday, in contravention of the NRL's biosecurity rules.
ARL Commission chairman Peter V'landys has told AAP the pair's actions must be a wake-up call, given the incidents place the whole game at risk.
Dragons chief executive Ryan Webb also didn't miss, claiming Vaughan had let the club down.
"Paul is one of our most experienced players and we are upset with his judgement in breaking the NRL's COVID-19 biosecurity protocols," Webb said.
"Not only has he let the playing group and the entirety of our hard-working staff down but also our Red V members, partners and fans."
Australian Associated Press