The World Cup veteran had been on course to appear in his third successive tournament.
Australian defender Lucas Neill has been dropped from Ange Postecoglou's squad for the upcoming World Cup in Brazil.
The veteran defender, who had captained his country through much of the qualifying campaign, was told by his manager that he hadn't quite made the cut, despite a move to the Championship in February in order to find the playing time that would secure a spot.
Neill had been winding down his career in the J League with Omiya Ardija, and moved to Watford at the start of the year to find the high level game time needed to secure a place in the Socceroos' World Cup squad.
But the move didn't turn out well, and a series of injuries saw him sent out on loan to strugglers Doncaster Rovers. In his whole time back in England Neill only turned out 5 times, a desperate disappointment for a player so formidable earlier in his career in this country, where the defender starred for Millwall, Blackburn Rovers and West Ham among others.
"I had a conversation with Lucas regarding the World Cup squad and obviously before I announced the 30-man squad next week I thought it was important for me to speak to him directly," Postecoglou said.
"I informed him that he hasn't made the 30, from my perspective paying due respect to the fact that he's been the captain for six years and the captain of the World Cup campaign so far.
"It was difficult, he's worked damn hard to get himself ready and available. He's shown an enormous determination to go to this World Cup.
"You can see why he's played for his country as many times as he has and why he was a leader, he's gone down fighting."
It was a close run thing for Neill's inclusion: "Certainly from my perspective, if post-Christmas, from January onwards, if he'd had four months of football under his belt, I guess a different decision would have been made."