Ognenovski, 35, has suffered damage to the 'lateral cutaneous nerve of the thigh', according to an official club statement.
The veteran centre-back will join a trio of serious knee injury victims, Corey Gameiro, Ali Abbas and Nick Carle, on the sidelines for the duration of the campaign.
"It's disappointing to lose a player of Sasa's calibre for the rest of the season," head coach Graham Arnold said in a statement.
"I will be speaking with chief executive officer Tony Pignata to discuss suitable replacements."
Arnold, who flagged the possibility of losing Ognenovski for the rest of the season after Sydney 2-0 loss at home to Wellington on Sunday, is expected to enter the transfer market in January in search of much-needed reinforcements.
However, the Sky Blues' hopes of mounting a title challenge, which had appeared alive and well early in the tenure of the former Central Coast title-winning coach, are receding with each new injury suffered.
Sydney sit fifth on the table after Round 11, having lost two and drawn two of their past four matches. They host Adelaide United on Friday.
The veteran centre-back will join a trio of serious knee injury victims, Corey Gameiro, Ali Abbas and Nick Carle, on the sidelines for the duration of the campaign.
"It's disappointing to lose a player of Sasa's calibre for the rest of the season," head coach Graham Arnold said in a statement.
"I will be speaking with chief executive officer Tony Pignata to discuss suitable replacements."
Arnold, who flagged the possibility of losing Ognenovski for the rest of the season after Sydney 2-0 loss at home to Wellington on Sunday, is expected to enter the transfer market in January in search of much-needed reinforcements.
However, the Sky Blues' hopes of mounting a title challenge, which had appeared alive and well early in the tenure of the former Central Coast title-winning coach, are receding with each new injury suffered.
Sydney sit fifth on the table after Round 11, having lost two and drawn two of their past four matches. They host Adelaide United on Friday.