The 18-year-old young gun suffered the injury when in the first half of Sydney FC’s 1-1 draw against Newcastle Jets at EnergyAustralia Stadium last Sunday and was forced to leave the pitch in the 44th minute.

It is an untimely blow for Sydney FC and Petratos, who scored debut goal against Gold Coast United at Sydney Football Stadium on last month after forcing his way into the first XI and playing 16 games this season.

Coach Vitezslav Lavicka has used Petratos in an attacking role to great effect this season with his speed and creativeness now going to be missed in the wake of Alex Brosque sudden departure for Japan.

Petratos will immediately commence at intensive rehabilitation program with club medical staff.

Striker Mark Bridge (groin) will also miss tonight’s clash with Wellington Phoenix at Sydney Football Stadium.