The United Rugby Championship fixture between Ulster Rugby and Connacht Rugby on St Stephen's Day has been postponed.
The game, which was due to be played at the Kingspan Stadium in Belfast will not go ahead as scheduled after a number of positive Covid-19 cases within the Ulster Rugby squad.
The URC Medical Advisory Group liaised with Ulster and local health authorities and deemed that the fixture cannot go ahead as scheduled, the province said in a statement.
Tournament orgainsers will now consider available dates to reschedule the game.
Ulster added that ticket holders are advised that their tickets remain valid for the rescheduled fixture, and the Ulster Rugby Ticket Office will be in touch with options once the new date has been confirmed.
Other derby games between Munster and Leinster and the Ospreys and Dragons had previously been postponed.
It leaves Cardiff’s home game with Scarlets as the only remaining URC fixture to be played on Sunday.
In a URC game that did go ahead on Christmas Eve, Benetton confirmed their current superiority over Italian rivals Zebre Parma with a dominant 39-14 win.
In England, Sunday’s Gallagher Premiership programme plans to go ahead as scheduled with five games set to be played.
The competition’s round of matches is due to be completed by Monday’s game between Harlequins and Northampton.