Having made just one appearance so far in 2013-14, the club captain will stay on the sidelines for up to a fortnight after picking up a new problem in training
The veteran forward has not played since Round 1 due to a whiplash injury suffered in a head collision during the derby against Melbourne Victory.
The club has now confirmed he is set to also miss the visit of Western Sydney Wanderers to AAMI Park on Friday, and is also doubtful for a home match against Sydney FC on November 15.
Speaking before news of his latest injury emerged, Kewell defended his decision to stay in Melbourne to play golf on Sunday rather than fly up with his team to Brisbane to watch them play the Roar.
"I felt I was fully fit, I wanted to play, it was a decision by my manager (being rested) which I respected," he said.
"Okay, I went out and swung a club. What's the harm in that?"
Kewell was left out of Ange Postecoglou's 22-man Socceroos squad for the clash with Costa Rica on November 19 but the 35-year-old hasn't given up hope of representing Australia again and maintained the only way he could do that was by playing well for the Heart.
"You play well for Heart, you have a chance. But if you don't play well for Heart then you won't have a chance," Kewell said.
Goalkeeping great Mark Schwarzer was another glaring omission from Postecoglou's squad after the Chelsea custodian decided to retire from international football.
Kewell described Schwarzer's decision as a 'shock' and a 'shame' and thought the stalwart should have kept playing for the Socceroos.
"He's done so well not only for club but especially for country," Kewell said.
"I still believe he's our best keeper, I still believe he's playing at one of the greatest clubs in the world so there's no reason he shouldn't have done (kept going).
"I didn't see it coming, he's a player that takes football very seriously, he's only improved as he's got older and it's a shock.
"Maybe I will ring him up and ask him because I find it hard to believe."
Meanwhile, Kewell believes the Heart have been playing better than their winless start to the season suggests.
"It's been unfortunate, there's been occasions where we've played through teams and opened them up and the ball's just gone the wrong side of the post," he said.
"But that's football, you've got to make these corrections and I'm sure the players are fully aware of that and they're going to start to do the proper thing."