Milligan left Antonis with a deep cut to his forehead following an aerial challenge between the two players in the first half at Etihad Stadium.
Referee Peter Green, despite being just metres from the incident, took no action in the game, potentially leaving the Match Review Panel to retroactively ban the Victory skipper for violent conduct.
"The referee makes those decisions. It's his decision, not mine," Arnold said.
"You can't talk about the match review panel, otherwise you'll get in trouble. And you get fined. You should know that coaches in this league aren't allowed to have an opinion. Because otherwise we get fined.
"He's (Antonis) getting 10 stitches in his eye. He said to me at half-time that he couldn't see out of his right eye, it was all blurry, watering all the time. But he still went out and did a fantastic job."
Asked about the knee injury substitute Nick Carle suffered at the end of the game, Arnold said: "I think his season's over."
"That's three knees in four weeks. Medial (knee ligament). It's not looking great. It's a bit cruel, we've only got 13 or 14 players as it stands now."
With Carle potentially set to join Ali Abbas and Corey Gameiro on the long-term injury list, Arnold confirmed Sydney are stepping up their January recruitment plans.
"There's some money freed up now. Potentially we can bring in three very good European players. We've got the visa spots open. Couple are really good quality, Bundesliga, French first division."