Doncaster prop forward Ian Williams has died after he collapsed at training, the English Championship club have announced.
Williams, 27, who joined the Knights from neighbours Rotherham last summer, collapsed during a session at Castle Park and could not be resuscitated.
Williams, an Oxford graduate, made six appearances for his club, who said in a statement: "It is with great sadness that Doncaster RFC announces the passing of prop forward Ian Williams.
"Ian collapsed at training at Castle Park this morning and, despite the best efforts of the emergency response team, could not be resuscitated.
"We extend our deepest sympathies to Ian's mother Pippa, father Phillip and sister Helen and are working with a counselling team in the best interest of Ian's teammates.
"The club will be making no further comment at this time."