A fourth Betfred Super League fixture of the season has fallen victim to coronavirus.
Friday's round 11 fixture between Hull KR and St Helens at Craven Park has been postponed after three more Rovers players tested positive over the weekend.
That follows two positive tests last week while nine other players have been forced to isolate as close contacts.
Training at Hull KR has been postponed until Wednesday under the Rugby Football League's Multiple Cases Protocols, with a further round of PCR testing to be carried out then.
It could put a doubt over Hull KR's next scheduled fixture, which is the Hull derby at Craven Park on Thursday week.
Rovers coach Tony Smith, whose team are coming off the back of a shock win at Wigan, admitted in the build-up to last Friday's game at Wigan that Super League clubs may have to cope with the affects of the pandemic for years to come.
"It's going to continue to have an impact," he said. "This is our concern and worry of our sport.
"From all the information I've read, Covid is now part of our society and with its variants is likely to have an impact for the next two or three years.
"How our sport is going to cope and live with it over the next couple of years is something that we need to work out if we're going to remain viable as a sport and also financially viable as a sport."
Hull KR players who had been selected for the Combined Nations All Stars team have been stood down as part of the isolation procedures.
A statement from the RFL said: "Under the RFL's coronavirus protocols, a team can apply to postpone a match if seven or more senior players are unavailable as a result of Covid-19 – either through positive tests or as close contacts – and the RFL has therefore accepted Hull KR's request to postpone Friday's fixture."
The clubs will liaise with the RFL on a possible date to rearrange the match later in the season – 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.
It is the second time St Helens have had a recent match called off. Their away fixture with Leeds fell victim to the pandemic after an outbreak in the Rhinos camp.
Leeds' trip to Catalans Dragons was also postponed while Huddersfield's home game against Wigan was called off due to an outbreak of Covid in the Giants camp.
Leeds have confirmed they have had no further positive tests, with players returning to training on Monday.
A statement read: "Following the latest round of PCR tests on Saturday, there were no further positive tests in the Rhinos squad. Those players available will return to training this morning. The eight positive players will follow the RFL's return to play protocol over the next week."
