Title-winning left back Michael Zullo was an absentee on Saturday night when Arnold switched former Socceroo Luke Wilkshire to that position for his Sydney debut, bringing in ex-Melbourne City man Paolo Retre – who he described as the bargain buy of the season – in at right back for his first start for the champions.
But Zullo's injury is not serious enough to keep him out on Wednesday, Arnold said, and he would play.
"He could have played (against Victory) if it was a grand final or a crunch game. But we've got three games this week and with hamstrings you always leave it a little bit longer."
For South Melbourne, Wednesday's game at Lakeside is the biggest it has been involved in for years.
Bill Papastergiadis, chairman of the South committee, which is agitating for a spot in the A-League, says the club has a chance to make a real statement of intent when it faces the current champions.
"We want to get a big crowd, to show that we have the support base, and we want to show that we can be competitive on the field as well," said Papastergiadis.
"Sydney are the champions, they are a very good team, but we are hoping to cause a big upset.
"At the start of the season we put a priority on doing well in the FFA Cup, and to reach the semi-final is a great achievement but we want to go even further if we can. "
It will be a daunting task for the Victorian underdogs as Arnold said after Saturday night's win that his Sydney team was currently only around 30 per cent as good as it could be.