MELBOURNE (AFP) - Defending champion Stan Wawrinka was on Friday pitted in the top half of the draw at the Australian Open with Novak Djokovic and faces a potential semi-final encounter with the world number one.

The Swiss fourth seed upset Djokovic in the quarter-finals on the way to winning his first Grand Slam title in Melbourne last year.

The Serb top seed is scheduled to face big-serving Canadian Milos Raonic in the quarters while Wawrinka could meet Japanese fifth seed Kei Nishikori in the last eight.

Roger Federer, who is chasing an 18th Grand Slam victory at 33, is on course to face Andy Murray in the quarter-finals in the bottom half of the draw.

Murray, a three-time Australian Open runner-up, lost to the Swiss great in the 2010 Melbourne Park final.

Federer, who will face Taipei's Lu Yen-hsun in the opening round, is the second seed.

Third seed Rafael Nadal faces a tough first-up opponent in Russian Mikhail Youzhny and could play big-serving Czech Tomas Berdych in the quarters in the bottom half of the draw.

Australian warhorse Lleyton Hewitt, playing in his 19th consecutive Australian Open, has drawn Chinese wildcard Zhang Ze in the opening round.