Mocking impressions, underarm serves, and verbals - Nick Kyrgios and Rafael Nadal have one of the most personal rivalries in tennis.

And the latest edition lands on Monday, with the two facing off at the Australian Open for a place in the quarter-finals.

Kyrgios is the polarising 24-year-old Australian with a penchant for rubbing up his illustrious opponent - world number one Nadal - the wrong way.

The pair will meet in Monday's fourth-round match at 08:00 GMT (19:00 local time) on Rod Laver Arena.

Somebody pass the popcorn. And, to use Kyrgios' stinging description of the Spanish great, make it "super salty"…

Nadal and Kyrgios 'go about it completely differently'

In terms of career achievements, Nadal is in a different league to Kyrgios.

The 33-year-old Spaniard has won everything the sport has to offer in a glittering career - which has brought 19 Grand Slam titles and automatic entry into every serious conversation debating who is the greatest male player of all time.

Kyrgios, meanwhile, is still to transfer a precocious and natural talent into mounting serious challenges for the biggest titles.

In a nutshell, that is why the pair haven't seen eye-to-eye.

Nadal's meticulous pursuit of success dominates every area of his life. He allowed himself a 24-hour honeymoon after marrying long-term partner Xisco Perello in October.

The more relaxed demeanour of Kyrgios, who can often be spotted in the local bars and pubs after Grand Slam matches, is a stark contrast.

And it irks Nadal.

"At the end of the day, we're two different tennis players. We go about it completely different," says Kyrgios, who is seeded 23rd.

Kyrgios has previously described Nadal as "super salty", while Nadal has been visibly irritated by the Australian's erratic on-court behaviour in the past.

To add further spice, Kyrgios cheekily mocked Nadal's superstitious service routine in his second-round win over France's Gilles Simon.

"I don't really know Rafa. I've never hung out with him or anything like that," Kyrgios said after his third-round win over Russia's Karen Khachanov.

"I don't really dislike him. I don't know him at all. I'm sure he's OK."

Re-sale tickets for the keenly-anticipated match on the 15,000-capacity Laver are close to A$500 (£260), according to Australian newspaper The Herald, even eclipsing the price of those for the in-demand National Rugby League and Australian Football League grand finals.

How the rivalry sparked

It all started back in 2014 when Nadal - then ranked number one, as he is now - was beaten by a fresh-faced 19-year-old Kyrgios in the Wimbledon last 16.

Ranked 144 in the world, Kyrgios wowed the Centre Court crowd when became the first man outside the top 100 to beat the world's best player at a Grand Slam since 1992.

Wild celebrations, speeding through service points and outrageously-timed 'tweeners - all still regular features of his high-octane matches - came to the fore for the first time.

Tensions between the pair barely simmered over the next few years as meetings in Rome, Madrid, Cincinnati and Beijing passed without major incident.

Then, in February 2019, it all started going down in Acapulco.

Nadal was furious with Kyrgios's underarm serving as the Australian won a tight three-setter. That led to a frosty handshake at the net and then, when speaking to the media afterwards, the Spaniard accused Kyrgios of lacking respect.

A few weeks later, Kyrgios took his opportunity to hit back. That seemed to be triggered by Nadal's uncle and former coach Toni claiming Kyrgios "lacked education".

In an interview with the 'No Challenges Remaining' podcast, Kyrgios said: "He's my polar opposite. Literally my polar opposite. And he's super salty.

"When he wins, it's fine, he won't say anything bad, he'll credit the opponent - 'he competed well today, he's a great player' - but then as soon as I beat him, it's just like 'he has no respect for me, my fans and no respect to the game'."

And then, in July, the pair met again at Wimbledon…

Wimbledon meeting didn't disappoint - can Melbourne match it?

The narrative around the build-up to their second-round match at the All England Club was, like here at Melbourne Park, that a potential blockbuster was brewing.

It didn't disappoint.

Kyrgios tried to hit Nadal in the chest with a return, complained about the time taken by the Spaniard between serves and angrily berated umpire Damien Dumosois.

While Kyrgios provided the fire, Nadal turned up with ice and let his tennis do the talking in a four-set win.

Since then, Kyrgios has started to do the same.

That behavioural change has been somewhat enforced by a six-month probation period, meted out by the ATP Tour in the shape of a suspended 16-week ban after another bad-tempered performance in Cincinnati.

"When he does stuff that in my opinion is not good, I don't like it," Nadal said.

"When he plays good tennis and he shows passion for this game, he is a positive player for our tour."

Will Australia unite behind a changed Kyrgios?

Kyrgios has produced plenty of positivity over an Australian summer which has seen his country marred by devastating bushfires, even though he is quick to make it clear his achievements shrink into insignificance comparatively.

The Canberra-born player teared up at the recent ATP Cup when he discussed the disaster.

That came after he pledged to donate 200 Australian dollars for every serve he hit this month, a gesture which sparked a huge fundraising effort among his fellow pros.

The total raised by the sport stood at over A$5.6m (£2.9m) on Sunday night.

Underneath the combustible on-court behaviour, Kyrgios clearly has a layer of tenderness and empathy which often comes to the surface.

And this charitable gesture - for which he says he does not "care about getting praise" - has seen him receive more backing from an Australian public which has not always warmed to him.

In front of a passionate and supportive Melbourne Arena crowd, Kyrgios showed immense mental strength to beat Russian 16th seed Khachanov in a five-set thriller which had the carrot of a meeting with Nadal dangling at the end.

Now he is aiming to extend his 2-1 winning record on hard courts over the 2009 champion to reach the quarter-finals and match his best Grand Slam run.

"There's a layer of respect that we both have for each other," Kyrgios said.

"He's one of the greatest of all time. I also read that he thinks I'm good for the sport.

"It doesn't necessarily mean we like each other, but we're going to go out there and give contrasting styles and personalities."