St Helens have confirmed that England hooker James Roby will be out for up to 10 weeks after discovering he will need to undergo ankle surgery for the second time this year.
The 27-year-old sustained ligament damage in the early stages of Sunday's 40-24 win at Castleford Tigers, which was only his fifth Super League match back after recovering from a similar injury.
Roby was out for two and a half months after damaging his other ankle against Wakefield Trinity Wildcats in March.
St Helens coach Nathan Brown said: "We're disappointed to lose a player of James' calibre but once again it presents an opportunity for another member of the first-team squad to step up and cement their place."
Brown is likely to turn to either Lance Hohaia or Stuart Howarth for the hooking role in Saints' next match, which is a derby against Wigan Warriors at Langtree Park on Monday, July 22.
Today's news is also a blow for England coach Steve McNamara, who re-affirmed Roby as his first-choice hooker when putting him straight into the team to play the Exiles last month, just two games into his comeback.
Roby will now be sidelined until the middle of September, just six weeks before the opening World Cup match against Australia.