Hull FC's fixture against Castleford Tigers this weekend has been postponed after their positive tests for coronavirus, while Salford's game against Catalans Dragons has also been postponed by the Super League.
Hull FC put their squad and coaching staff into isolation after six players, five of whom played against Salford in the 54-18 defeat on Sunday, tested positive for Covid-19, alongside two members of their coaching staff.
The Black and Whites' Challenge Cup quarter-final on August 22 - also against Castleford - will take place at a later date after that too had to be postponed.
Catalans Dragons' sixth-round match with Wakefield Trinity, which had been due to kick off at 5pm as the second part of a double header at the John Smith's Stadium in Huddersfield, has been brought forward to a 2:30pm kick-off.
Hull were informed of their positive tests by Public Health England on Tuesday evening, before both teams cancelled their scheduled training sessions for Wednesday.
A sixth member of Hull FC's playing squad at the weekend is having a retest after an inconclusive result.
Salford have returned negative tests, however, the Red Devils squad will self-isolate.
All players and relevant support staff from Hull FC and Salford, with the exception of those Hull FC players and staff members who have already tested positive, had additional tests on Friday, with results due the next day.
The full weekly breakdown of results will then be made available when those results have been received.
Saturday's scheduled fixture between Salford and Catalans will not go ahead, along will Hull's game against Castleford on Sunday.
The fixture reshuffle means Super League will now instead hold a behind-closed-doors double-header on Saturday and Sunday at St Helens' Totally Wicked Stadium, live on Sky Sports.
Catalans now face Wakefield Trinity at 4.15pm on Saturday in a fixture which was postponed earlier in the season due to Storm Ciara and Castleford's scheduled Round 16 match against St Helens has been brought forward to this Sunday at 4.15pm.
That has seen the two other fixtures for this weekend shifted as well. Warrington Wolves will now play Huddersfield Giants at 6.30pm on Saturday, and Wigan Warriors and Leeds Rhinos will meet at the same time on Sunday.
The revised fixture list for August 15-16 is as follows:
- Saturday, 4.15pm: Wakefield Trinity vs Catalans Dragons
- Saturday, 6.30pm: Huddersfield Giants vs Warrington Wolves
- Sunday, 4.15pm: St Helens vs Castleford Tigers
- Sunday, 6.30pm: Wigan Warriors vs Leeds Rhinos
Super League executive chairman Robert Elstone said: "Throughout this crisis our priority has been to ensure we minimise any risk, and the postponement of this weekend's scheduled fixtures involving Hull FC and Salford underlines that approach.
"It left us with another challenging situation, but it is a credit to the solidarity of the Super League clubs who agreed to adjust the fixture list at such short notice.
"We also appreciate the ongoing support and flexibility of our broadcast partner and are pleased that we remain able to present four great Super League fixtures this weekend, all live on Sky Sports."