Former Castleford and Great Britain winger St John Ellis, the coach of Doncaster, has died at the age of 41.
Ellis was a big favourite of the Castleford fans
He suffered a suspected heart attack after taking the National League One club for a pre-season training session.
Attempts were made to resuscitate him and he was rushed to hospital where he was pronounced dead. He leaves a wife, Melanie, and two young daughters.
"It's a great shock to us all. His heart stopped and he never recovered," said Doncaster chairman John Wright.
"We had the physio there and other trained people who tried to give him mouth to mouth straight away, but it was no good.
"You wouldn't believe it. There wasn't a fitter coach in the game. He was a fitness fanatic who never asked any of his players to do something he couldn't do himself."
Ellis played for Castleford, Bradford, Halifax, Keighley, Hunslet and Doncaster before taking over as coach of the South Yorkshire club towards the end of the 1999 season.
He was a member of the Castleford side which lost to Wigan in the 1992 Challenge Cup final at Wembley and won three Great Britain caps from 1991-94.
Assistant coach Tony Miller has been placed in temporary charge of the Lakers.