One is the top ranked player in the world and the other, seeded 16th, is arguably the best player in the sport. And the two of them will meet in a blockbuster fourth round clash of the Australian Open.

But no matter what the rankings say, top seed Simona Halep is considered the underdog going into her match against 23-time Grand Slam champion Serena Williams.

The 37-year-old American, playing just the eighth tournament in the 10 months since her return from maternity break, has dropped only nine games in three matches so far in the first Slam of the year. On the other hand, the 27-year-old Romanian endured torrid two matches and was not a 100% fit heading into 2019, losing five matches on the trot in curtailed 2018 season since US Open last year.

Serena also has a dominant 8-1 winning record over her younger opponent.

But don’t let that fool you. Halep is the strongest competition Serena has faced early in the three Grand Slam she has played after her return in her quest to get a record equalling 24th Major.

While Serena has lost to sister Venus, Petra Kvitova and Johanna Konta since her return, the Serena juggernaut was only stopped in Major finals – Angelique Kerber at Wimbledon and Naomi Osaka at US Open. Everyone else she faced early were cannon fodder – Karolina Pliskova in New York, Julia Goerges at Wimbledon being the highest seeds she overcame.

And on Saturday, Serena crushed Ukrainian Dayana Yastremska 6-2, 6-1 before consoling her at the net as the teenager burst into tears; not the first opponent to break down after facing the “Serena-tard” clad 16th seed.

Last year’s runner-up Halep was equally dominating in her third round encounter against Venus as he finally hit top form to win 6-2, 6-3. She played a near flawless game with only 12 unforced errors while overpowering the 38-year-old.

But is the win against Venus enough to show that Halep can really push the 2017 champion?

Serena has a big serve and powerful groundstrokes but Halep has the ability to run and chase everything and is likely to put more balls in play and test the American’s patience and fitness. Because if the error-prone Halep from the first two matches shows up, Serena will have all the weapons to exploit the chinks in her armour.

Ready for the challenge

Their responses ahead of the match also shows a contrast: the top seed seeing it for the challenge it will be and Serena relishing it.

“Yeah, not easy. I just have to give my best. I have nothing to lose, I play against a great champion. It’s going to be a bigger challenge but I’m ready to face it,” Halep said in a measured response.

But Serena, who has the second-most wins (16) over World No 1s in WTA history, seemed a lot more at ease as she said: “I honestly would love to face the world number one, it will be great. I haven’t played the world number one since I’ve been back [from having a baby], so, yeah, it will be good.”

The only two times they met at Grand Slams, the matches went to three sets with Serena winning both. In fact, their last match was the US Open quarter-final in 2016.

But much water has flown under the bridge since then: the Romanian has climbed up the ranks to the very top, backed that up with her first Grand Slam title at the 2018 French Open, and showed a lot more confidence and consistency on the tour.

Halep admitted that she is not overawed by her opponent anymore, despite the lopsided head-to-head. “When I was younger, but now I don’t feel intimidated any more. I have huge respect for her because she’s a great champion, but she’s just an opponent next round,” she said.

Mental game as much as physical

That is exactly the kind of mentality needed to take on someone like Serena. Against a slower Venus, she was aggressive and swift and took her chances, unlike the first two rounds.

She said that this will be her game plan in the next round as well, but Serena is at a much higher level physically. The plan will be to target her on the run and make her play that extra ball to force an error.

But for Serena this will be the test to prove where her game is at. She hasn’t played since the US Open last year, except for the Hopman Cup where she won all her matches.

In the two Grand Slam matches she has lost since her comeback, she was poor on serve against Kerber who got the angles right while Osaka hit through her with natural power and aggression. Halep might look at a combination of this but a strong mental game will be the most important aspect – a weakness that has often hindered her in the big matches.

The Romanian may not have coach Darren Cahill anymore for much-needed tactical guidance but she has her Fed Cup captain and another Romanian coach with her, and her former coach could also help when he is not working as an analyst.

Whatever game plan they device together, there is no doubt that Halep will have to play near flawless service games and wear down Serena’s big serve.

With her penchant for lung-busting rallies, Halep has the advantage of endurance. But if Serena keeps the match on her racquet, then her powerful strokes could end up dictating the result.

Either way, this will be a titanic clash for women’s tennis.