On a day where John Isner, Philipp Kohlschreiber and Radek Stepanek were among those who failed in the Melbourne heat on Tuesday and either retired hurt or didn’t make it onto court, Australia's world No. 1 Hewitt showed his incredible fighting spirit up against Italian 24th-seed Andreas Seppi.
However, Roger Federer, Andy Murray, Juan Martin Del Potro, Jo-Wilfried Tsonga, Kei Nishikori, Milos Raonic, Yen-Hsun Lu, Grigor Dimitrov, Fernando Verdasco, Feliciano Lopez and Victor Hanescu have been among the men to win through the second round in Day 2 action so far.
It wasn’t a good start for the Australians either with James Duckworth and Marinko Matosevic both losing, albeit as expected, to Federer and Nishikori respectively but then Kyrgios scored a terrific four-set win over Benjamin Becker before Hewitt went down in five sets.
The night then ended for the Australians with Kokkinakis prevailing in four sets over Dutchman I Sijsling while Bernard Tomic retired against Rafael Nadal after losing the first set 6-4.
Earlier, Seppi went up two sets to love against Hewitt but the Australian showed his trademark fighting qualities to win the next two sets and then again fight back from falling down a break to start the fifth, but the Italian just prevailed in the finish 7-6 (4), 6-3, 5-7, 5-7, 7-5 in over four hours of action.
Hewitt earned an early break in the first set against Seppi, but the Italian immediately broke back and the set went into the tie-break with Seppi dominating to win it seven points to four.
Seppi then looked to be right on top of the match when he cruised through the second set 6-3, but the 32-year-old Hewitt was not ready to give and it certainly wasn’t easy in the third and fourth sets.
However, he managed to win them both seven games to five to force a fifth set.
It was the 12th time Hewitt has played a five-setter at the Australian Open and remarkably the eighth time in the opening round.
Despite winning the third and fourth sets, Hewitt then again found himself needing to find something with Seppi racing out to a 2-0 and 3-1 fifth set lead with an early break.
Hewitt fought hard, though, and in the eighth game managed to break back to tie things up at four games apiece and things moved to being 5-5, but Seppi then scored the match-deciding break and held on to it to take the set 7-5 to claim the four hour, 18-minute marathon on Rod Laver Arena.
Meanwhile, one Australian did win through to the second round on Tuesday with 18-year-old world No. 183 Nick Kyrgios scoring an impressive upset win over Germany's Benjamin Becker in four tight sets.
The young Australian won 6-3, 6-7 (5), 6-2, 7-6 (2).
The next headline Australian act then became Kokkinakis on Court 3 against Sijsling.
The Australian 17-year-old won the first set in a tie-break but when he failed to win a game on the way to losing the second it appeared that winning the first round at a Grand Slam was a step too far at this point of his career.
However, he had other ideas and again won the third set in a tie-break and then cruised through the fourth to wrap up the match 7-6 (4), 0-6, 7-6 (3), 6-2.
John Isner became the biggest casualty of the second day with the No. 13 seed forced to retire with a foot injury on a hot Melbourne day after losing the first two sets against Slovak world No. 106 Martin Klizan.
Isner had good form leading into the Australian Open having won for the second time at the ASB Classic in Auckland, but he had a nagging foot injury from Perth's Hopman Cup and it flared up again on Tuesday.
However, the American 17th-seed was being outplayed anyway with Klizan already leading 6-2, 7-6 before Isner retired from the match and tournament.
It caps off a run of good luck for the former world No. 26 Klizan who is currently ranked 106 and only made it into the Australian Open because Spain's Nicolas Almagro was a late withdrawal, but now he is through to the second round with his upset over Isner.
Australian 21-year-old James Duckworth tried his best to give Roger Federer a fight, but the world No. 133's best was well below that of the Swiss master with Federer cruising into the second round winning 6-4, 6-4, 6-2 on Rod Laver Arena.
France's 10th-seed Jo-Wilfried Tsonga cruised through his last two sets after a tight first set battle on Hisense Arena against Italian Filippo Volandri with the former Australian Open finalist winning 7-5, 6-3, 6-3.
Australian Marinko Matosevic put up a tremendous fight against Japan's No. 16 seed Kei Nishikori with the battle going to five sets, but in the end the Japanese seed had just enough to come out victorious 6-3, 5-7, 6-2, 4-6, 6-2.
Poland's Michal Przysiezny scored a three-set victory over Argentina's Horacio Zeballos despite the last two being tight, winning 6-3, 7-6, 7-5.
Frenchman Stephane Robert had to win his first set in a tie-break against Slovak Aljaz Bedene, but he then cruised through the next two sets to book a spot in the second round, winning 7-6, 6-3, 6-0.
Canadian 11th-seed Milos Raonic dropped the third set against Daniel Gimeno-Traver and had to win the first in a tie-break, but he made it through to the second round with a 7-6, 6-1, 4-6, 6-2 victory on Court 8.
Court 11 hosted a battle of two Chinese Taipei players fighting out for a second round appearance and it was the more fancied Yen-Hsun Lu who beat Jimmy Wang in straight-sets, 6-3, 6-2, 6-1.
Rising Bulgarian star Grigor Dimitrov became the first player of the day in the scorching conditions to come back from a set down to win, beating American Bradley Klahn 6-7, 6-4, 6-4, 6-3 in an impressive showing from a player that continues to show so much potential but is yet to put it all together.
It was another four-set battle between Serbia's Dusan Lajovic and Frenchman Lucas Pouille on Court 20 with Lajovic winning 6-4, 7-6, 4-6, 6-3.
Romanian veteran Victor Hanescu is also through to the second round beating German Peter Gojowczyk in straight-sets, even though two were tie-breaks, 7-6, 7-6, 6-3.
Three-time Australian Open runner-up and No. 4 seed Andy Murray had no trouble winning his opening round match beating Japan's Go Soeda 6-1, 6-1, 6-3.
World No. 5 and former US Open winner Juan Martin Del Potro surprisingly lost the first set in a tie-break to American Rhyne Williams, but controlled the contest from there to win 6-7 (1), 6-3, 6-4, 6-4.
Spanish veteran Fernando Verdasco also had to overcome losing the first set against his opponent, but the left-hander was able to do so beating China's Ze Zhang 5-7, 6-3, 6-2, 6-3.
French No. 27 seed Benoit Paire was on top of Canada's Frank Dancevic after winning a first set tie-break that lasted 22 points, winning the match 7-6 (12), 6-3, 6-4.
Russian Teymuraz Gabashvili also overcame losing the first in a tie-break to beat Ukrainian Sergiy Stakhovsky 6-7 (3), 6-4, 6-2, 6-0.
Czech Republic veteran Radek Stepanek started strongly on Court 13 up against Slovak Blaz Kavcic winning the first two sets, but he then lost the third and was down a break in the fourth before retiring in the fourth.
That handed victory to Kavcic 6-7 (3), 4-6, 6-1, 2-0.
American Donald Young beat Dutchman Robin Haase with yet another retirement 6-7 (4), 7-6 (2), 6-2, 1-0.
Spanish veteran Feliciano Lopez had an easier time of it with the 26th-seed beating Indian Somdev Devvarman in straight-sets, 6-4, 6-4, 7-6 (2).
Frenchman Gael Monfils was expected to have a tough battle up against American Ryan Harrison on Margaret Court Arena, but he ended up prevailing impressively in straight-sets 6-4, 6-4, 6-4.
The men's action for Tuesday then wrapped up with two five-set battles.
The marathon of the Australian Open so far took place out on Court 7 and the fifth set alone lasted one hours and 55 minutes with the match lasting four hours and 32 minutes as Gilles Simon eventually prevailed against German Daniel Brands 6-7 (4), 6-4, 3-6, 6-3, 16-14.
Despite being hobbled by ankle complaint, Frenchman Simon continued to fight but the 18th-seed was playing catch up most of the match against the German.
In the 20th game of the fifth set with Brands leading 10-9, he had four match points on the Simon serve but he couldn’t get the job done as the Frenchman continued to show good fight.
After he held on in that game, the match lasted 10 more games before Simon eventually was able to break Brands' serve and that proved the difference in the finish as he won the fifth set 16-14.
Those missed break and match points will be something that will continue to haunt Brands for some time to come as he only managed to convert 2-of-25 break point opportunities while Simon took his chances better with 4-of-10.
The other five-set battle took place between Croatia's Marin Cilic and Spaniard Marcel Granollers on Court 8.
Granollers was well on top winning the first two sets, but he couldn’t close it out with the big-hitting Croat fighting his way back into the contest and managing to win the last three sets to take out the match 4-6, 4-6, 6-3, 6-3, 6-2.