Roger Federer showed his readiness to fill the Murray-Djokovic-shaped hole at the Australian Open by outclassing Kei Nishikori in five sets to make the quarter-finals.

While the top two players in the world leave Melbourne, a chance for Federer to add to his 17 major titles has opened up, and this performance at Rod Laver Arena was a reminder that he remains capable of replicating his full repertoire of brilliance, Nishikori going down 6-7 (4-7) 6-4 6-1 4-6 6-3.

Federer let his emotions show after wrapping up victory, an indication perhaps that he believes number 18 could be on the cards.

World number five Nishikori took the opening set on a tie-break, after Federer had fought back from 5-1 down, a stunning backhand that just took some paint with it earning the Japanese the crucial mini-break in fine fashion.

Momentum had swung Federer's way in a five-game winning run, however, and the second set was a nail-biting affair, both players scrapping hard from deep before a Nishikori double fault cost him dearly in a set of no other chances.

Now with his tail up, Federer served out for 1-1 with just seven shots and he took the lead in a punishing set for the 2014 US Open finalist, Nishikori's second serve a constant avenue for Swiss success as the great master took just 26 minutes to move in front, echoing his swift destruction of 10th seed Tomas Berdych in the previous round.

Nishikori showed sensational grit to force a decider - somehow holding serve as Federer forced him to cover all angles of the court - another stunning passing shot, this time forehanded, doing the business for Nishikori.

But Federer's class told in the fifth, catching a physically struggling Nishikori off guard with a fizzing forehand that the Japanese could only net for an immediate break before checking off a few hallmarks - numerous serves up the tee, and a backhand around the net among them - en route to victory.

Mischa Zverev is next up for Federer and Andy Murray's demise at the hands of the German will put the 35-year-old on red alert, but a potential semi-final with compatriot Stan Wawrinka is already a mouth-watering prospect.