The fullback is facing a lengthy stint of rehabilitation after suffering a serious knee injury in pre-season with his Eredivisie outfit
Zullo's Dutch club FC Utrecht confirmed the injury on Twitter, after the 25-year-old twisted the joint awkwardly at training.
It's a cruel blow for Zullo, who was seeking to establish himself in the Utrecht first team after spending last season on loan in the A-League with Adelaide United.
"I immediately felt that something was wrong," Zullo said on Sport Promotion.
"I hope it's not too serious and I'm out for most of the year."
Zullo, who missed out on a spot in the Socceroos' World Cup squad, is in the final year of his deal with the Dutch club.
Yesterday it was confirmed that first-choice Socceroo defender Matt Spiranovic will have an operation on his ankle and will be out for around 10 weeks.