Novak Djokovic will contest his 23rd consecutive grand slam quarter-final after easing past Luxembourg journeyman Gilles Muller 6-4, 7-5, 7-5 at the Australian Open.

Djokovic was pushed by the 42nd-ranked Muller, a big-serving left-hander with the shots to rally with the top seed, but the four-time champion was almost bullet-proof on serve and cut the 31-year-old down repeatedly when he rushed to the net.

Earlier, Kei Nishikori matched his career-best performance at Melbourne Park by grinding down David Ferrer 6-3, 6-3, 6-3 to reach the quarter-finals as well.

Japan's number one will meet defending champion Stan Wawrinka for a place in the semi-finals.

Wawrinka avenged his early exit at last year's French Open with a 7-6, 6-4, 4-6, 7-6 victory over Guillermo Garcia-Lopez to book his place in the last-eight.

Later, Milos Raonic struck a blow for the next generation of male players by felling Spanish veteran Feliciano Lopez 6-4, 4-6, 6-3, 6-7, 6-3 to reach his first Australian Open quarter-final.

Eighth-seed Raonic became only the second Canadian to reach the last eight at Melbourne Park, nearly 50 years after Michael Belkin achieved the feat in 1968.

Quarter-finals:

Novak Djokovic v Milos

Stan Wawrinka v Kei Nishikori

Rafa Nadal v Tomas Berdych

Andy Murray v  Nick Kyrgios

Source: Reuters