* Neill faces fight to win back armband
* Postecoglou says retired Schwarzer was in his plans
* New coach cuts defender Wilkshire in clean-out (Adds details, quotes, changes dateline)
SYDNEY, Nov 6 (Reuters) - New coach Ange Postecoglou took an axe to Australia's ageing squad after back-to-back 6-0 defeats plunged their World Cup preparations into chaos, but said Mark Schwarzer had been in his plans until the veteran goalkeeper's shock retirement from the national side earlier on Wednesday.
Postecoglou, who replaced the sacked Holger Osieck after humiliating losses to Brazil and France, has retained defender Lucas Neill but stripped him of the captaincy while 32-year-old Luke Wilkshire was among a clutch of ageing players to be cut.
Postecoglou, seeking to rejuvenate a demoralised team eight months out from the 2014 World Cup finals in Brazil, announced the changes in naming his first squad ahead of Australia's Nov. 19 friendly against Costa Rica.
While former Blackburn Rovers captain Neill retains his place amid calls for him to retire, the 35-year-old defender is on shaky ground and may owe his spot to the loss of Schwarzer's experience and leadership.
Neill will have to prove himself in an intensive training camp before the Costa Rica match in Sydney and faces a tough battle to win back the captain's armband he has worn since 2006.
Postecoglou named midfielders Mile Jedinak and Mark Milligan as potential leaders, but 33-year-old striker Tim Cahill is the frontrunner for the captaincy.
"I look at this list and there's some good leaders in there," Postecoglou told reporters in Sydney.
"It's imperative I've got all those players, experienced ones, to step up. I've never seen the captaincy as something that is crucial to what I build.
"To me it's more about the team."
Postecoglou took the reins last month after unpopular German Osieck was sacked following consecutive 6-0 losses to Brazil and France in friendlies.
While Osieck steered Australia to their third consecutive World Cup finals, Football Federation Australia boss Frank Lowy cited his failure to regenerate the ageing team following the 2010 World Cup in South Africa as a key reason for his dismissal.
Postecoglou has little time to rebuild before Brazil but has made an early start, shedding defensive stalwart Wilkshire and overlooking 34-year-old central defender Sasa Ognenovski, left back David Carney and midfielder Brett Holman, both 29.
However, the 41-year-old Schwarzer had been included in the initial 22-man squad, Postecoglou said, despite missing the team's recent friendlies against France and Canada.
"I've got the utmost respect, firstly for his decision and secondly it would be remiss of me not to pay tribute to him," Postecoglou said of Chelsea's backup keeper, who bows out with a record 109 appearances for Australia in a glittering 20-year international career.
"He's no doubt one of our all-time greats."
Schwarzer had long stated his goal was to bow out with a third successive World Cup in Brazil but passes the mantle to either Mitchell Langerak or Belgium-based Mat Ryan.
Borussia Dortmund's Langerak is widely tipped to take Schwarzer's spot against Costa Rica, who have also qualified for the World Cup.
South Korea-based defender Alex Wilkinson earns his first call-up after enjoying solid form in the K-League, while midfielder Tom Rogic has been recalled after recovering from injury.
(Reporting by Ian Ransom in Melbourne; Editing by Peter Rutherford)