Liam Henry will undergo knee surgery and miss the rest of the 2024 season.
"Scans today have shown Liam has significant cartilage damage to his knee," St Kilda executive general manager of football David Misson said.
"Liam has had a rough run with injuries this year which has been disappointing, but we've also been able to see the impact he can have when he is up and running, so we're confident that after this period of rehab we'll see Liam back to his best in 2025."