KR's home game against St Helens, scheduled for this Friday, was postponed earlier in the week after five players had tested positive for Covid-19 and with nine others required to isolate as close contacts.
However, a further eight players have now tested positive for the virus and have therefore been required to begin isolation periods of 10 days, at which point the players would be able to return to training under the Gradual Return to Play Protocols programme which takes an additional seven days.
Four members of backroom staff are also self-isolating after testing positive, and the club are awaiting the results of a further round of testing.
A Super League statement confirmed a new date for the Hull derby but there has been no confirmation on when the Robins will play St Helens or Catalans.
"It has been agreed that Hull KR v Hull FC will be rescheduled for Thursday July 15 – with live coverage on Sky Sports (kick-off 7.45pm)," read a Super League statement.
"Whilst the usual starting point is that matches are rearranged in chronological order, it is not possible for St Helens to play on this weekend as they are in the Betfred Challenge Cup Final.
"Discussions regarding possible rearrangement of the other two outstanding Hull KR fixtures – against St Helens and Catalans Dragons – will continue, although the Betfred Super League table will again be determined by win points percentage to allow for the possibility of not all fixtures being fulfilled."
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