Sia Soliola signed for St Helens from Sydney Roosters last May
St Helens winter arrival Sia Soliola will miss the rest of the season after suffering a torn knee ligament injury - just two games into his Saints career.
The 23-year-old Kiwi, who only returned to the team on Sunday after ankle trouble, suffered his latest blow in training on Wednesday.
Saints lost Soliola's team-mate Paul Wellens for a month earlier this week.
"This is a real blow for the team and we are naturally disappointed for Sia," said Saints coach Mick Potter.
He added: "He will now undergo a long rehab programme and we are all behind him.
"But, as with last season, injuries also present the opportunity for younger players in the squad to step up and we will once again utilising the versatility of our squad."
Soliola, who signed for Saints 10 months ago from Sydney Roosters, arrived at Knowsley Road over the winter and made his debut at centre in the opening day 32-12 home defeat by Hull FC.
He then missed five games with an ankle ligament injury before returning at second row in Sunday's 28-18 win over Warrington.
Full-back Wellens will be out for a month after suffering a torn thigh muscle against Warrington.