De Jong – on loan at Sydney from Ajax in the Netherlands – pulled up lame just 20 minutes after coming off the bench.
He clutched his thigh in agony and coach Steve Corica was caught on camera swearing furiously in disgust when he realised the extent of the problem.
de Jong made an instant impact for Sydney when he scored a stunning free kick in the earlier derby clash in the FFA Cup when the Sky Blues smashed the Wanderers 3-0.
Corica had hoped to keep de Jong wrapped in cotton wool ahead of this week's FFA Cup Final, but he was quickly ruled out of playing any part in the decider against Adelaide United on Tuesday night.
Now though the club has revealed he is unlikely to be back until just before Christmas.
The 29 year old arrived at Sydney with a long injury history behind him including two collapsed lungs as well as a series of calf and groin injuries and several long term thigh and hamstring injuries.
One thigh straight saw him out of action for 145 days, while another hamstring injury saw him miss 24 games.
After Saturday's game, Corica admitted: "We put him on the bench to rest him and not give him 90 minutes, because I wanted him to be fresh on Tuesday night.
"Unfortunately it didn't work out that way."