It's a funny thing being world No.1 in this changeable era of women's tennis. Amid the honour of reigning as the world's best, there's also the pressure of holding on.
Simona Halep, in that top spot during a Grand Slam for the first time, has already demonstrated both the pride with which she regards her position and her determination to cling tight to it at AO2018.
Ousted in the first round in the past two Australian Opens, the 27-year-old Romanian has fought her heart out to overcome some inspired opponents and an ankle injury to return to the fourth round for the third time.
In Saturday’s titanic third-round battle with world No.76 Lauren Davis, Halep showed a new level of resolve as she saved three match points to secure a 4-6 6-4 15-13 win.
"It's the only one match that I played like this," said Halep. "It was not easy, but I just kept playing. I just kept believing that it's not over, even if she's leading a little bit more."
Played over three hours and 44 minutes, it wasn't quite the longest women's match in AO history – that record secured in Francesca Schiavone's epic win over Svetlana Kuznetsova in 2011, which required one hour longer – but tied the Open era record set by Chanda Rubin and Arantxa Sanchez Vicario in their 1996 quarterfinal for the most games played.
Halep's coach, Australian Darren Cahill, described his charge's win as a rollercoaster of the most pleasing kind. "I'm not sure I've sat through a more emotional tennis match, in all my years of coaching," he said.
Managing such emotion was an important turning point for Halep, who has let some big opportunities slip in recent times. She led Jelena Ostapenko 6-4 3-0 in her second appearance in a French Open final last year before the Latvian stormed back to win. Halep also featured in what many regarded as the match of the year at the 2017 US Open, but it was the returning Maria Sharapova who won their first round in three sets.
"I think in the past I wouldn't have fought that hard," said Halep after withstanding 52 winners from Davis in Melbourne. "Maybe when she had the match [points], maybe I would have lost it. But now I improved in that way and it makes me really happy that I changed myself in a good way."
If mentally stronger, there are physical worries for Halep, even aside from the typical recovery challenges created by such an energy-sapping win.
The ankle she rolled in the first round against Destanee Aiava was heavily strapped and managed with painkillers on Saturday, and is unlikely to significantly improve within days. "It's sore. I felt the pain," Halep admitted. "After this match, I think tomorrow is going to be worse."
Then, of course, there's yet another inspired another opponent, with Naomi Osaka waiting in the fourth round. The 20-year-old has defeated two seeded opponents – No.16 Elena Vesnina and No.18 Ashleigh Barty – to progress so far at a Slam for the first time.
"Osaka is hitting strong, so strong," said Halep. "I have to be strong, if I can, on my legs, and just stay there, playing fast, opening the court."
Halep is the winner of both matches she's contested against Osaka – at the French Open in 2016 and Miami in 2017 – but both have required three sets. "I feel like I learned a lot," said the Japanese world No.70. "I feel playing the No. 1 is really an honour. No matter what happens, I'll try my best."
Osaka is not the only fourth-round debutante at AO2018. Fresh from his five-set upset of No.4 seed Alexander Zverev, 21-year-old Korean Hyeon Chung returns to face Novak Djokovic for a second time, after the pair also competed in the first round of AO2016. Hungary's Marton Fucsovics, who had never won a Grand Slam main draw match before this tournament, plays a career-first match against defending champion Roger Federer.
It would seem a monumental task for Chung or Fucsovics, ranked world No.58 and No.80 respectively, to oust either former champion – still, both Djokovic and Federer will be on guard.
As the top-ranked Halep has discovered, the highest-profile targets can experience the most spirited fights.