Friday's game between Huddersfield and Wigan is in serious doubt as Covid-19 once again threatens to cause major disruption to the Betfred Super League.
The PA news agency understands the Giants have reported at least five positive cases which would be enough to force them to close down training and take them to the brink of postponing the round nine fixture at the John Smith's Stadium.
A decision is thought to be imminent on what would have been Huddersfield's first home game in front of fans for 15 months.
It will be the first fixture of the 2021 Super League campaign to fall victim to the coronavirus pandemic, which caused havoc with the 2020 season and prompted the Rugby Football League to rule that league positions would be determined by win percentages.
The amended format was maintained for this season and extended to both the Championship and League 1 with the likelihood of more fixtures being postponed and unable to be re-arranged.
The Championship match between Halifax and Sheffield Eagles in May was postponed after two Eagles players returned positive tests and five more were forced to isolate under track and trace regulations.
Sunday's Women's Super League derby between St Helens and Wigan has been called off after a Saints player tested positive in the wake of Saturday's Challenge Cup final victory over York and more than five of her team-mates were ordered to self-isolate for 10 days.