St Helens have confirmed that hooker James Roby will be out of action for 10 weeks with an ankle injury.
The 27-year-old suffered the problem when at Castleford on Sunday and now requires surgery to resolve the issue.
Head Coach Nathan Brown told the club's official website: "We're disappointed to lose a player of James's calibre but once again it presents an opportunity for another member of the first team squad to step up and cement their place."
Roby's predicted layoff time will leave him with just one month to try to grab a place in the England squad for the World Cup, which begins on October 26.
