Perth, Jan 3 (Reporter) World No.1 Novak Djokovic overcame a wrist problem to defeat Jiri Lehecka in three sets, as Serbia beat the Czech Republic to set up a blockbuster United Cup quarterfinal with host Australia. Serbia's comeback 2-1 victory on Tuesday powered them to the top of Group E in a result that means China will play top seeds Poland in an intriguing quarterfinal on Wednesday. Serbia will face Australia in the night session of the double header at RAC Arena...////...