Saints have confirmed forward Alex Walmsley tore a knee cartilage in their Semi Final victory over Catalans, but played through the pain in the Grand Final.
The England International was seen struggling with a knee injury against the Dragons, but his determination to help Saints win back to back Super League crowns saw him strap it up and opt to play through the pain in the Grand Final on Friday.
Walmsley, who marked his 200th Saints game with a third Grand Final ring, will now undergo surgery to correct the issue.
The club say they are confident he should return in time for the 2021 season, which will start in March.