Australians Nick Kyrgios and Sam Groth are through to the third round of the Australian Open for the first time.

Kyrgios, the top-ranked local hope, outplayed 23rd seed Ivo Karlovic 7-6 (7-4) 6-4 5-7 6-4 for his best result at an Australian Open.

The big-serving Groth defeated 19-year-old compatriot Thanasi Kokkinakis 3-6 6-3 7-5 3-6 6-1. It is the furthest Groth, 27, has progressed in a grand slam tournament.

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Owner of the world’s fastest-ever serve, Groth crunched 26 aces to chisel out a memorable victory over one of Australian tennis’ next big things.

“I feel like I’m in career best form and I’m where I’m at in the rankings for a reason,” Groth said.

“I’ll come back firing on Friday.”

The 27-year-old’s reward is a clash on Friday against Bernard Tomic in another all-Australian showdown after he saw off German 22nd seed Philipp Kohlschreiber 6-7 (5-7) 6-4 7-6 (8-6) 7-6 (7-5).

The grand slam hosts are now assured of second-week singles participation.

Tomic’s tournament appeared to be coming to an end when he dropped the opening set in a tiebreak and trailed Kohlschreiber 3-1 in the second set.

But, unlike his first-round mid-round stoppage against Rafael Nadal last year, Tomic refused to quit.

Even after recovering to take the second set to draw level, the 22-year-old repeatedly found himself under pressure.

Time and again he stared down break points and, at one stage in the pivotal third-set tiebreak, even three set points.

Seemingly on each occasion, Tomic’s clutch serving saved him.

He racked up 23 aces in all.

If not his serve, Tomic’s big, flat forehand came to the rescue in the pressure moments as he eventually prevailed after three hours and five minutes.

Kokkinakis was valiant in defeat against Groth.

After upsetting world No.13 Ernests Gulbis in his first-ever five-set match on Monday night, Kokkinakis again threatened to pull off a mighty comeback win from two sets to one down.

But the 18-year-old appeared to twinge a hamstring early in the deciding set as the higher-ranked and more-experienced Groth raced to a 5-0 lead before advancing after two hours and 53 minutes.

Meanwhile the 19-year-old Kyrgios didn’t appear to be bothered by a back injury which hampered his preparation and first-round win over Argentina’s Federico Delbonis.

He also toned down the theatrics in a calm and controlled performance.

If he can see off Tunisia’s world No.75 Malek Jaziri on Friday, the 19-year-old will likely take on Roger Federer in a blockbuster battle for a quarter-final spot.

Jaziri beat Frenchman Edouard Roger-Vasselin 1-6 6-3 6-4 1-6 6-3.

Among the Australians who lost on Wednesday were James Duckworth who went down 6-2 6-3 7-5 to Richard Gasquet, the tournament’s 24th seed, before sixth seed Andy Murray stopped Marinko Matosevic 6-1 6-3 6-2.

Despite his friendship with Matosevic, Murray said pre-match that he was out to break Australian hearts.