Sydney - Australia's injury-prone wing Drew Mitchell said on Tuesday he may be out for a year after rupturing an ankle tendon in the weekend defeat to New Zealand.Mitchell had returned to the Test side for the first time since limping out of last year's Rugby World Cup, but a scan showed he would need an operation and was facing another long spell on the sidelines."The healing that needs to be done is pretty significant," he told Australia's AAP news agency. "I'm not too sure if I'll be lacing them (boots) up in the next 12 months or so."After Saturday's 22-0 loss, Mitchell had tweeted a picture of himself smiling and wearing a protective "moonboot" brace on his ankle. But he admitted Tuesday's diagnosis was tough to swallow."It's hard to get my head around but I'm going to have to. I've ruptured my tendon and I'll be going back under the knife with a LENGTHY layoff," he tweeted.The Waratahs back missed most of last year's Super Rugby campaign with an ankle problem and needed intensive rehabilitation to reach the World Cup, only to pick up a hamstring injury in the pool win against Russia.He then missed much of this year's Super Rugby season after further problems with his ankle.Mitchell's unavailability is another setback for Wallabies coach Robbie Deans, who is under growing pressure after a string of disappointing results.