Alex Walmsley has been ruled out for the long term after fracturing a bone in his neck during Saints recent win over Warrington.
The 27-year-old came off the field in the second half of the match at the Halliwell Jones Stadium.
Saints head coach Justin Holbrook said: “It is obviously a massive blow to our team given the fact that Alex is the best front rower in Super League. He has been in great form already this year after a good World Cup.
“But importantly, the news that Alex will make a full recovery from the injury is one we all welcome.
“Alex has had an operation to correct the damage and will now begin his recovery led by our medical team. We all wish him well.
“The surgeon has told both Alex and the Club that he will make a full recovery and his neck will be stronger than ever.”
He continued: “We want to wish Alex a speedy and safe recovery and can’t wait to have him back on the field with the boys – but only when he has fully recovered.
“We have a strong squad at Saints and I’m sure that the rest of the team will step up in Alex’ absence.”