Spiranovic has been a mainstay in Australia's central defence and a key part of coach Ange Postecoglou's FIFA World Cup and Asian Cup squads.
But the China-based 28-year-old was a notable omission in an extended 30-man line-up for this month's crunch World Cup qualifiers, with Postecoglou revealing a "complicated" pre-season quad injury could be a long-term concern.
"He picked up an injury in pre-season and he'll be out for a significant amount of time," Postecoglou said.
"It's still not clear, the extent, but the early signs we have is that he'll be missing for a little while.
"He wasn't even in consideration."
The injury is a blow for Spiranovic in a year packed with qualifiers, Confederations Cup and a high-profile friendly with Brazil.
But Postecoglou admitted Spiranovic would have been up against it regardless, trying to prove his fitness and form from China's second division.
The coach made it clear the country's second-tier standard wasn't up to scratch back in October when Spiranovic's club Hangzhou Greentown were relegated from the Chinese Super League.
But instead of moving elsewhere for better-quality football, the former Western Sydney Wanderers fan favourite decided to see out his contract with Hangzhou.
As it stands, Milos Degenek and regular pair Bailey Wright and Trent Sainsbury have been selected, though the latter is a touch-and-go prospect given he hasn't been playing for Italian giants Inter Milan.
Versatile Perth Glory defender Rhys Williams also earned a surprise recall at the expense of Sydney FC's Alex Wilkinson, though Postecoglou was quick to clarify Wilkinson's commanding A-League form has kept him in calculations.
"I took him to the last World Cup so I'm aware of his abilities, and he has had a very good season for Sydney," he said.
"He's still on our radar. Sometimes it's just about continuing that good form.
"There's no reason to say when the next squad comes around he wouldn't be picked."