The Dewsbury-born St Helens forward, such a hit in the World Cup, fractured a bone against Warrington Wolves recently and has undergone surgery.
“It is obviously a massive blow to our team given the fact that Alex is the best front rower in Super League,” said St Helens coach Justin Holbrook.
“But importantly the news that Alex will make a full recovery from the injury is one we all welcome.
“The surgeon has told both Alex and the club that he will make a full recovery and his neck will be stronger than ever.”
Elsewhere, organisers are pressing ahead with plans to take a Super League fixture to America, but face a race against time to enter a New York club in English competition in 2019.
It is six months since a consortium submitted an application to join the Championship, but they are still waiting to get the go-ahead.
An RFL delegation visited New York in January and has asked for more details about the business plan of the proposed new club who will still try for 2020 even if time does run out.
Meanwhile, talks are ongoing with the Red Bull Arena and US broadcasting companies about taking a Super League game to New York later this year and Ricky Wilby, the Englishman fronting the bid, says the consortium will cover all costs of the travelling teams.
Salford have expressed a willingness to switch one of their home games to the Big Apple and, although an initial proposal to move their Good Friday fixture with Catalans Dragons has fallen through, Wilby says there are two other Super League clubs keen to become involved.
Warrington have completed the signing of ex-Wigan Warriors and England winger Josh Charnley from Sale Sharks on a three-year deal.
Halifax host Oldham in the Ladbrokes Challenge Cup tonight while Featherstone Rovers welcome North Wales Crusaders after both ties were postponed due to the bad weather at the weekend. Hunslet Hawks’ Challenge Cup game against Bradford Bulls has been rearranged for Easter Monday.