Torino fear the worst after centre-forward Duvan Zapata was stretchered off in tears during the 3-2 defeat to Inter, as his left knee appeared to buckle.
The 33-year-old had found the net for 10-man Toro at San Siro following the Guillermo Maripan straight red card just 20 minutes into the match.
He was alone battling against two Inter defenders when trying to turn, but his left knee seemed to simply buckle under him.
Duvan Zapata was visibly distraught and immediately feared the worst, so both teammates and his Inter opponents crowded around to console him.
Torino risk losing Duvan Zapata for the season
It had been a strong start to the campaign for the striker, who has four Serie A goals in seven games, plus one in two Coppa Italia appearances.
The former Atalanta man had a series of bad injury problems in recent years, above all muscular.
The initial reports do suggest a probable anterior cruciate ligament tear, which if confirmed would require surgery and around six months out of action.
Torino have a lot of serious knee ligament injury issues, already losing Perr Schuurs last season, Emirhan Ilkhan and Zanos Savva this term.