The Betfred Super League match between leaders Catalans Dragons and Warrington at the Halliwell Jones Stadium on Thursday has been postponed just over seven hours before kick-off.
The Dragons said four members of their essential staff have tested positive for coronavirus within the last 24 hours, three of them on Thursday morning shortly before the squad were due to fly to England.
Super League said consideration will be given to rearranging the fixture, but that seems unlikely with only seven weeks left of the regular season.
A total of 21 Super League fixtures have been postponed this year and only four of them have so far been played at a later date.
It is the fourth Catalans game to be postponed due to Covid but the first due to an outbreak in their own camp.
The table will again be determined by win points percentage to allow for the possibility of not all games being fulfilled, with clubs required to complete 70 per cent of their fixtures in order to qualify for the play-offs.
The Catalans have already reached the threshold but Warrington need to play two more to meet it.
The game, between the teams placed first and third in the table, was due to be televised by Sky Sports, who did not have enough time to switch their coverage to the Leeds-Huddersfield match.
Warrington said tickets can be transferred to the club's next home fixture against St Helens.
Newcastle's Betfred Championship fixture with London Broncos on Sunday has also been postponed because Thunder have at least seven senior players ruled out either as a result of positive Covid-19 tests or as close contacts who are not fully vaccinated.