The pain of losing to city rivals Western Sydney Wanderers at home is now compounded by injury for Sydney FC with young star Rhyan Grant ruled out for the rest of the season due to a knee injury.

It might only be round three but the midfielder has already played his last game for the season after rupturing his anterior cruciate ligament in his knee during the club’s lacklustre 2-0 loss to their cross-town rivals on Saturday night.

Dejected: Nikola Petkovic and Seb Ryall after Sydney FC's loss on Saturday night. Credit:Getty Images

The club feared a lengthy lay-off for the highly rated 22-year-old after he was left in agony after he jarred his knee in a routine challenge in the first half against the Wanderers, and had to be helped off the field.

Grant underwent scans on Sunday which confirmed the worst. He will now likely have to undergo surgery and be forced to endure a lengthy spell on the sidelines.