Ronaldo has announced his retirement from football after an 18-year career . The two-time World Cup winner said the decision was down to injury and a lack of fitness . He will be replaced by former Real Madrid striker Iker Casillas who is expected to take over as manager in January 2013. Mentally , I wanted to continue , but I have to acknowledge that I lost ( the fight ) to my body , '' a visibly upset Ronaldo said . The medication required to treat the illness is banned under football 's anti-doping rules .
Ronaldo has announced his retirement from football after an 18-year career . The two-time World Cup winner said the decision was down to injury and a lack of fitness . He will be replaced by former Real Madrid striker Iker Casillas who is expected to take over as manager in January 2013. The medication required to treat the illness is banned under football 's anti-doping rules .