Top-seed Novak Djokovic overcame a nervous start and feisty Fernando Verdasco to safely negotiate his way into the fourth round of the Australian Open.

With the surprise loss of Roger Federer still hanging over the men's draw, Djokovic was well aware the danger the 31-year-old Verdasco, a former top-10 player posed.

The Spaniard had taken Rafa Nadal deep into the night in a five-hour, five set marathon during the 2009 semi-finals in Melbourne and only trailed the Serb 6-4 in their career head-to-head record.

Verdasco harassed Djokovic at the start but once the world number one sealed the first set tiebreak after an hour of the tense baseline battle he ran away with the match in the next two to win 7-6, 6-3, 6-4 and set up a fourth round clash with Luxembourg's Gilles Muller.

Earlier, defending champion Stan Wawrinka sealed comfortable victory over Finland's Jarkko Nieminen.

The 29-year-old Swiss, appearing on Rod Laver Arena virtually 24 hours after Federer had been shocked by Andreas Seppi on the same court, did not allow the tricky lefthander any opportunities to do the same in the 6-4, 6-2, 6-4 win.

Other results (selected):

Gilles Muller (Luxembourg) beat 19-John Isner (U.S.) 7-6(4) 7-6(6) 6-4 

5-Kei Nishikori (Japan) beat Steve Johnson (U.S.) 6-7(7) 6-1 6-2 6-3

12-Feliciano Lopez (Spain) beat Jerzy Janowicz (Poland) 7-6(6) 6-4 7-6(3)

8-Milos Raonic (Canada) beat Benjamin Becker (Germany) 6-4 6-3 6-3

Source: Reuters