Anthony Seibold will sit out Brisbane's next two games and a fortnight's training after leaving the club's NRL bubble for personal reasons.
Seibold opted to stay in NSW after his team's loss to South Sydney, with Broncos chief executive Paul White pointing to a "serious family matter".
Given he has left the bubble, he will now need to self-isolate for 14 days on return to Brisbane with assistant Peter Gentle to take charge.
"Anthony is dealing with a serious family matter and could not fly back to Brisbane with the team after the Rabbitohs game last night," White said.
"He expects to be able to return to Brisbane within 48 hours but in line with COVID regulations he will need to self-isolate for 14 days once he is back in Queensland.
"Anthony will return to the Broncos after that. Assistant Coach Peter Gentle will coach the team in Anthony's absence.
"We are working with Anthony to give him all the support he and his family need at this time, and we ask media to respect his privacy."
Queensland have some of the toughest border rules in the country, with anyone who has visited NSW forced to enter into two weeks' isolation.
NRL teams have exemptions to fly across the border, but they must remain in their bubble and return the same day without staying overnight.
It is the latest chapter in what has been a bizarre week in the NRL and the toughest year in the Broncos' history.
Wayne Bennett was on Thursday forced out of his club's bubble and fined $20,000 by the NRL for eating out at an inner-city restaurant.
He missed the Rabbitohs' win over his former club, and will not be able to return until his two weeks away from the team are complete.
Brisbane legend Allan Langer and two other fellow support staff also missed the match and were fined $5000 fot attending a function last weekend.
Their error now threatens to leave the Broncos heavily depleted for football staff in the bubble.
The club have won just one of 11 matches since their return from the COVID-19 shutdown, and are at a serious risk of collecting their first wooden spoon.
Their defence is the worst of any team through the first 13 rounds of any team in four years, while their 3-10 start is also the worst in the club's history.
Australian Associated Press