What is Safin's peak? Two tournaments, USO 2000 and AO 2005? In those two tournaments, Safin played out of his mind, and beat some great players. His match against peak Fed (personally, 2005 Fed's tennis level was his best, even better than his 2006 form) was a tennis classic. Therefore, Safin would be more than capable of beating Djokovic. 2005 AO Safin vs 2011 AO Djokovic would be a spectacle. I am not sure who would be the winner in that hypothetical match, but it would definitely be a 5 setter.