Nick Kyrgios (Australia) d Andrea Seppi (Italy) 5-7 4-6 6-3 7-6 (7-5) 8-6
Tomas Berdych (Czech Republic) d Bernard Tomic (Australia) 6-2 7-6 (7-3) 6-2

Nick Kyrgios, the endearingly confident teenager who grabbed our attention at Wimbledon, has in a matter of months turned into something on an entirely different scale.

Not a monster, but something decidedly scary. Scarily good, scarily brave, scarily erratic, scarily out there.

• Click on the owl to see the quarter-finals 
• When Eugenie met Maria: Daily Deuce, day seven
• Pro’s choice: why Lleyton will know when it’s time

The 19-year-old was on display in all his various guises on Sunday during his exhilarating five-set win over Italian Andreas Seppi, making him the first Australian since Lleyton Hewitt a decade ago to make the men’s quarter-finals in Melbourne.

By the end of the three hour, 34 minute epic, in which Kyrgios came back from two sets down and survived a match point in the fourth set, he had the Hisense Arena crowd in a state of fist-pumping frenzy, the like of which has rarely been seen in Australian sport.

Smashes his racquet …

Kyrgios has, in fact, become the biggest showman in world tennis.

For some sportsmen, the crowd is incidental; for Kyrgios, it is integral.

Some play as if in a bubble; Kyrgios plays as though on stage in a pantomime, entreating the audience to join him in creating an overwhelming force in which player and crowd feed upon one another.

Together, Kyrgios and the crowd survived countless nervous moments and the support emboldened the Australian to attack without pausing to consider the consequences.

After fighting his way back into the match with a brilliant third set, Kyrgios survived match point in the fourth set tie-breaker with a thundering 201 km/h ace. He then sealed the set with an exquisite down-the-line backhand, one of his finest shots of the night, taking the match into a fifth.

The 30-year-old Seppi, for all his competence, was virtually anonymous, a level-headed ball returning machine for the scatty, hyperactive risk taker in fluoro.

But after hanging on magnificently against a seemingly inexorable force, the Italian wilted in the 14th game of the fifth set, which he lost to love to concede the match.

Goes between his legs …

From his haircut to his habit of watching himself on replay, Kyrgios is acutely conscious that this is not just sport – it is performance.

But it is far from scripted. On the contrary, no one – including Kyrgios – knows what will happen next.

There were enough outbursts and curious occurrences to keep a sports psychologist engaged for months.

Among them:

• Asking the crowd and, presumably, himself: “Why is everyone sleeping right now?” and later screaming “Wake up!”

• Telling a linesman: “You’ve got one line to work on, right? One.”

• Discussing his back injury with the crowd, including: “I’m trying, man. I can’t walk though.”

• Performing a lairy scissor kick before what should have been a forehand put-away, only to see Seppi calmly return it for a winner. (He repeated the action later in the match, but this time managed to win the point.)

• Regularly commentating on Seppi’s precision strokes, including the pithy observation: “Lines, aces …”

Well played old chap …

• Smashing his racquet and earning a warning at the end of the first set.

• Attempting a gratuitous between-the-legs shot in the second set when, unlike against Rafael Nadal at Wimbledon, there was plenty of time to get around to play a forehand.

• Gesticulating theatrically for a Seppi ball to go long during the tense fourth set tie-breaker.

• Mocking a couple of fans for leaving during the fifth set.

• Over-ruling the linesman in an act of sportsmanship to give Seppi a point in the fifth set.

Kyrgios confirmed the obvious later when he said the crowd had played a big role in the win.

“It feels so good,” Kyrgios told the Hisense Arena. “This is my favourite court I’ve ever played on.”

He will now play Brtiain’s Andy Murray, who defeated Grigor Dimitrov and promptly described the Australian as dangerous, unpredictable and entertaining.

The win means Australia has one singles representative in the second week, following Bernard Tomic’s straight-set loss to Tomas Berdych.

Tomic had rather ungraciously complained after his match against big-serving Sam Groth that their contest was “not tennis”.

But if Tomic wanted a game of tennis he got one against Berdych, a consummate professional who has made the semi-finals of all four majors and commands respect.

To be fair to Tomic, Berdych started in blistering fashion, serving ferociously and producing an array of mighty groundstrokes.

When Tomic tried to the pace off the ball and employ his artistry, Berdych just slam danced him off the court. Few would have been able to survive the early onslaught.

When Berdych’s game went slightly off the boil it at least became a contest, with Tomic taking the second set to a tie-breaker.

The Australian produced some fine winners, but made too many leaden footed blunders to beat a player like Berdych, not least the straightforward forehand volley that crashed into the net and gave the Czech victory in straight sets.

After that, it was all up to Kyrgios. And how.

And, finally, overcome with emotion. Photos: Getty