Australian Open 2020: Rafael Nadal battles past gritty Nick Kyrgios to reach quarter-finals in Melbourne (VIDEO)

Spanish tennis superstar Rafael Nadal overcame an inspired performance by Australia's Nick Kyrgios to book his place in the last eight of the Australian Open with a four-set victory on Monday.

The world No. 1 eventually claimed victory 6-3, 3-6, 7-6, 7-6 after fending off a spirited challenge from Kyrgios, who showed bucketloads of grit and determination as he went toe to toe with the 19-time Grand Slam champion in Melbourne.

Nadal looked on course for victory after taking the first set, but soon realized he was in a shootout when Kyrgios fired back with a vengeance in the second set to level the match.

It set up a tense finale as the pair went back and forth through the third set, which Nadal edged via tiebreak, then the fourth, which saw Kyrgios fight back to save the match by breaking Nadal when he was serving for the victory.

The match went into a second tiebreak, but once again Nadal proved to have the edge as he won the set, and the match, after three hours, 38 minutes to book his place in a quarter-final clash with Austrian Dominic Thiem later this week.

Following his victory, Nadal hailed the performance of his opposite number, telling John McInroe: "What can I say about Nick? When he is playing like today, with this positive attitude, he gives a lot of positive things to our sport. So I encourage him to keep working like this, because he is one of the highest talents that we have on our tour."

And Nadal added his words to the ongoing tributes paid by the world's biggest sports stars to NBA legend Kobe Bryant, who had died in a helicopter crash the previous night.

Also through to the quarter-finals is Germany's Alexander Zverev, who snapped Russian star Andrey Rublev's 15-match winning streak and continued his run of not dropping a set in the tournament so far.

The No. 7 seed produced a superb display as he totally dominated proceedings with his serve, not facing a single break point during the entirety of his straight-sets victory, while securing a break of serve in each of the three sets to cruise to a 6-4, 6-4, 6-4 win.

Zverev, who hit 11 aces in the matchup, will take on Stanislas Wawrinka, who also eliminated Russian opposition in the Last 16. The former champion defeated Daniil Medvedev after a five-set thriller earlier in the session.

Zverev, who hit 11 aces in the matchup, will take on Stanislas Wawrinka, who also eliminated Russian opposition in the Last 16. The former champion defeated Daniil Medvedev after a five-set thriller earlier in the session.