Stevie Ward has ended his playing career at just 27 as a result of continued symptoms following two concussions last year.
Catalans Dragons set up a Super League play-off semi-final against St Helens with victory over Leeds Rhinos on Friday.
It remains to be seen when Castleford Tigers will be in action again after four more players tested positive for COVID-19.
Leeds Rhinos were without a host of key men at Wakefield Trinity, but they ground out a much-needed victory.
Super League strugglers Wakefield Trinity have discovered a rich vein of form and stunned COVID-affected Leeds Rhinos.
Salford Red Devils and Leeds Rhinos clinched victories in Monday's Super League action as St Helens and Castleford Tigers were beaten.
St Helens and Wigan Warriors were big winners in Friday's Super League action as Leeds Rhinos and Salford Red Devils felt their force.
Luke Gale struck with a drop-goal just four minutes from time to seal a narrow win over Salford Red Devils at Wembley.
Following two inconclusive test results each for Hull KR and Salford Red Devils, their game on Tuesday was delayed by an hour.
There were two hat-tricks at Headingley as Leeds and Salford followed up Challenge Cup semi-finals wins with Super League victories.