Kantarovski, 29, has not played since a five-minute stint off the bench in Newcastle's 3-0 victory against Wellington Phoenix on August 13, 2020, in the last round of their 2020-21 campaign.

The former Young Socceroos skipper underwent complex surgery in April last year to repair a problematic nerve in his lower back and sat out an entire season.

Despite extensive rehabilitation and physiotherapy, he has missed the first five rounds of 2021-22 and it is unclear when, or if, he will be able to resume.

It is understood he has been unable to join his teammates in full training.

Jets coach Arthur Papas has taken a patient and cautious approach with the club's most-capped player and remains hopeful that he can make a comeback later this season.

"Ben has been working hard to return to full fitness, but unfortunately he has suffered a couple of setbacks in his rehab," Papas told the Newcastle Herald.

"However we are still committed to supporting him and hopefully he can rejoin training with the first team in the near future."

Kantarovski, who debuted in the A-League as a 16-year-old and has represented his home-town club in a record 196 games, is off contract at the end of this season.

The playmaker told the Newcastle Herald last year he was hoping to avoid surgery, which he described as "a very last resort".

"That's quite a drastic and risky surgery, so we want to stay away from that avenue, but if it does come down to it, we may have to look at that," he said in March.

A month later, he underwent surgery but it has not provided a quick fix.

Injuries have been a constant source of frustration throughout Kantarovski's career.

Regarded as one of Australia's brightest young prospects when he debuted in the A-League in 2008, he needed a full reconstruction of his right knee in 2010, and had further surgeries on the same knee in 2012, 2014 and 2016.

He told the Herald last March that "the love of football" kept him going.

"There's nothing better than coming day in, day out to play the best sport in the world ... I can't wait to be back out there." he said.