Long overdue a change of luck on the injury front, 24-year-old Kokkinakis looked right at home back on centre stage as he traded blows with the 2019 Open semi-finalist before bowing out 6-7 (5-7) 6-4 6-1 6-7 (5-7) 6-4.

The No.5 seeded Tsitsipas did not drop a service game in a marathon encounter which lasted four hours and 32 minutes - the longest match of the tournament to date.

Tsitsipas was simply relieved to move into the third round, but praised Kokkinakis' talent and determination.

"Thanasi is a great competitor and a great fighter," he said.

"It was very difficult facing him. He's a talent, he has huge potential - pretty sure he knows it himself.

"He just needs to take advantage of it and make the best out of his career.

"He's a great server, has all the weapons from the baseline; despite the difficulty of the match, I really enjoyed being out here showing the world some really high-quality tennis."

Kokkinakis was able to make the match go the distance by stepping up in the two tiebreaks.

He also saved a match point in the 10th game of the fourth set.

The performance was all the more impressive considering Kokkinakis has battled a plethora of serious injuries in recent years, which has seen his world ranking plummet to No.267.

He also missed the 2020 Open due to glandular fever and then chose not to travel overseas to play last year due to the COVID-19 pandemic.

But when fit, the South Australian remains a formidable foe, as he proved when beating then-world No.1 Roger Federer three years ago at the Miami Open.

Kokkinakis' talent was on show time and again on Thursday night in a match watched by his close friend and doubles partner Nick Kyrgios.

Despite pushing Tsitsipas to the limit in a gruelling hit-out, Kokkinakis still turned out with Kyrgios for their first-round doubles encounter less than an hour after his singles match ended.

Kokkinakis and Kyrgios were first dubbed the Special Ks in 2013 when they squared off in the Australian Open junior final and appeared to have the tennis world at their feet.

Before Thursday evening, the previous time Kokkinakis had played on Rod Laver Arena at the Australian Open was in 2014 when he lost in straight sets to Rafael Nadal at the age of 17.

Tsitsipas will take on Mikael Ymer in the third round on Saturday after the Swede ousted Spanish teen sensation Carlos Alcaraz 2-6 6-4 6-4 7-6 (7-5).

Australian Associated Press