| Tennis News | Monday January 21 2013 6:35
Defending champ Novak Djokovic has been pushed to the limit before prevailing in a five set epic to reach the Australian Tennis Open quarter finals.
The Serb trailed Switzerland's Stan Wawrinka 6-1, 5-2 before rallying to win 12 -10 in the fifth set of a match lasting five hours and two minutes.
Djokovic will face Czech fifth seed Thomas Berdych for a place in the semis.
Auckland's ASB Classic champ Agnieska Radwanska has beaten Ana Ivanovic in straight sets to set up a quarter final against China's Li Na.
Maria Sharapova and Ekatarina Makarova are into an all Russian quarter final.