Sydney - Controversial Australian flyhalf Quade Cooper was on Tuesday ruled out of the remainder of the southern hemisphere Rugby Championship with damage to his recently reconstructed knee.Rugby officials said Cooper, 24, would miss Australia's final fixtures against Argentina and the Springboks after scans revealed a "small chip of articular cartilage in his right knee which will need to be attended to."Cooper had reconstructive surgery to the knee after a season-ending injury at last year's Rugby World Cup and the Wallabies said he needed a further operation to clean it out."It is not a long-term injury and so may not rule Cooper out of the Wallabies Spring Tour in November," team officials said in a statement."A decision on the flyhalf's availability for that trip will be made once his rehabilitation is underway."While unwelcome news for a side already hard hit by injury, with a number of key playmakers sidelined, Cooper's unavailability resolves a selection headache for under-pressure coach Robbie Deans.Deans admitted after Australia's lucky 23-19 escape over the Pumas on Saturday that he had considered bringing Cooper off, following a series of crucial errors including a wayward kick that led to an Argentinian try.The Wallabies were down 19-6 with 20 minutes left to play, and only two last-gasp runs over the line saved Deans from a loss that may have been terminal to his stewardship of the Australian side.The mercurial Cooper has been under heavy scrutiny since his inconsistent performance at last year's World Cup where he was relentlessly booed by Kiwi fans over alleged cheap shots on All Blacks captain Richie McCaw.He was not selected for Australia's first Bledisloe Cup match against New Zealand last month, and had few chances despite running on in the following match, which New Zealand snatched with a historic 22-0 thrashing.The Wallabies depart Australia on Thursday for their September 29 Test against the Springboks in Pretoria, finishing their Rugby Championship campaign with a game against Argentina the following week.They are currently ranked second in the four-nation tournament behind New Zealand.