Great Britain scrum-half Sean Long is almost certain to miss the Gillette Tri-Nations Series.
The 28-year-old has a fractured left cheekbone, it was confirmed on Tuesday, and will be out for a minimum of six weeks.
He sustained the injury in a challenge by Wigan hooker Terry Newton during last Friday's 38-12 win at the JJB Stadium and will undergo reconstructive surgery later this week.
He will be the fifth player to withdraw from Great Britain coach Brian Noble's initial squad, which has been depleted by the loss of Paul Sculthorpe, Kris Radlinski, Paul King and Newton.
Saints suffered a double blow on Tuesday with confirmation that Australian winger Darren Albert also sustained a cheekbone fracture in the same match will miss the club's bid to reach the October 15 Grand Final.
"It's disappointing for both players because this group is pretty tight and they do feel for each other," said coach Daniel Anderson. "It was quite sombre on Friday night but there is a resilience about the club and we have some boys here who will step up.
"You do want your big guns for the play-offs. We'll just have to knuckle down and work as a unit."
Carl Jones, a consultant facial surgeon, said: "Sean Long has a fracture of the left cheekbone with involvement of the eye socket, while Darren Albert has a fracture of the right cheekbone with possible involvement of the eye socket."
While Albert's injury was the result of an accidental collision with Wigan full-back Brett Dallas, Saints suspect foul play in the case of both Long and second rower Lee Gilmour, who was carried off on a stretcher with concussion after being tackled by Newton.
The Wigan hooker, who was put on report for the challenge on Gilmour, is facing the Rugby League disciplinary committee later on Tuesday on two separate charges of striking.
Anderson was still angry on Tuesday over the incidents, which he compared to the bad old days of rugby league.
"I've been in rugby league for a while and I saw some incidents there that I have never seen before as a coach," he told a news conference at Knowsley Road. "It reminded me of the old school rugby league.
"It's a tough game and you get some reckless and careless acts but I haven't seen too many incidents of that voracity and that intention.
"We have to protect our players. You don't get many opportunities in your career to be in big games and, when they are taken away by accident or by deliberate nature, it's a disappointment and, of course, everyone here is quite shattered by the injuries to the boys. But football is a contact sport and they are resilient to move on."Like