Partick Thistle midfielder Ryan Stevenson is to have an operation following the knee injury he picked up against Hamilton Academical.
The Scottish Premiership club say the full extent of the cartilage damage is unclear and that they therefore cannot put a timescale on his recovery.
"The scan showed that Ryan had suffered a medial meniscus tear," said the Thistle website of the 30-year-old.
"Ryan is due to go in for surgery tomorrow afternoon."
Thistle added that, after the operation, their medical team "should have a much better idea of whether he will be fit to return in time to go through a full pre-season".
Stevenson, who will miss Thistle's final two games of the season, signed a two-year contract when he joined the Glasgow club after leaving Hearts in June 2014.
Hamilton defender Michael Devlin is being sent to a specialist after also picking up a knee injury during Saturday's 1-1 draw on Accies' synthetic pitch.
Thistle striker Kallum Higginbotham criticised the New Douglas Park surface following the game.
Dundee United midfielder John Rankin and St Johnstone manager Tommy Wright have also since criticised artificial surfaces.
However, Hamilton player-manager Martin Canning has insisted that his players enjoy playing on a surface he views as "the way forward" for Scottish football.