Sunday night's Celtic Crusaders versus Wakefield game in the engage Super League was postponed due to the death of Wildcats player Leon Walker in a reserve team fixture.
The announcement came just 35 minutes before the match in Bridgend was due to kick-off.
The 20-year-old player, who was in his first season with Wakefield, is thought to have suffered a heart attack during the Wildcats reserves' match against their Crusaders counterparts at Maesteg on Sunday.
Eye witnesses reported the player going awkwardly into a tackle, getting to his feet and playing the ball before then collapsing.
Attempts were made on the field to revive him and the match was abandoned after 63 minutes while he was airlifted to the Morriston Hospital in Swansea, where he was pronounced dead on arrival.
The Rugby Football League took the decision to postpone the Super League match between the two clubs. Initially no reason was given for the decision, other than "unforeseen circumstances", because the player's parents had not been informed.
Wakefield chairman Ted Richardson said: "This is a tragic loss for all involved within rugby league. Clearly everybody at the club is devastated by this news and all our sympathies and prayers are with his family at this time."
RFL chief executive Nigel Wood said: "This is truly shocking and tragic news and our heartfelt condolences go to the parents, family and friends of Leon as well as the Wakefield Trinity Wildcats club. Our thoughts and sympathies are with all those involved at this devastating time."
Walker joined the Wildcats from Salford City Reds on a one-year deal in November.
The second row or loose forward joined Salford from Leeds amateur club Churwell Chiefs and during his three years with the Manchester club earned representative honours at academy level with Yorkshire and England in 2007.
Sunday's death is the latest in a series of tragedies to hit the Wakefield club in the last 10 months.
The Wildcats players have dedicated this season to the memory of popular prop forward Adam Watene, a Cook Island international who collapsed and died of a heart attack during a weight training session in October at the age of 31.
The club were already mourning the sudden death of Great Britain and Wakefield legend David Topliss, who collapsed during a five-a-side football match in June at the age of 58.
And the club also lost two members of their 1968 Challenge Cup final team during 2008.
In August Don Fox, who was the Lance Todd Trophy winner in their Wembley defeat by Leeds, lost his long battle with illness and in December centre Ken Hirst passed away.
Wakefield's next scheduled match is against St Helens at Belle Vue on Friday and a decision is expected to be made on Monday on whether it will go ahead.