The rivalry between Simona Halep and Angelique Kerber is all square at 4-4. It dates back to October 2009, when an 18-year-old Halep (ranked No.228) faced top-seeded Kerber (ranked No.95) in the first round of an ITF $50,000 event in Saint-Raphaël, France - and upset her 5-7, 6-2, 7-5. (Halep would make the quarterfinals of the tournament, falling to eventual champion Pauline Parmentier.) Halep would win their first three encounters, also winning the 2014 Doha final and in the third round of Toronto in 2015.
In 2016, Halep and Kerber would play five times. Though the Romanian would once again triumph in Canada, capturing their Montréal semifinal, it was this year that the German began to turn the rivalry around, winning on four occasions, all in straight sets: in the Fed Cup World Group play-off on Halep's home turf in Cluj-Napoca, the quarterfinals of Wimbledon, the semifinals of Cincinnati and in round-robin play at the WTA Finals.
Caroline Wozniacki and Elise Mertens have faced each other just once before: their Australian Open semifinal will reprise their Bastad semifinal last July, won by the Dane 7-5, 4-6, 6-2.
Each of the Australian Open semifinalists this year has reached a final this year already. Angelique Kerber triumphed at Premier level, winning the Sydney International (as well as leading Germany to the final of the Hopman Cup); Simona Halep and Elise Mertens both lifted International trophies at the Shenzhen Open and Hobart International respectively; and Caroline Wozniacki was the runner-up to Julia Goerges at the ASB Classic, Auckland. Kerber, Halep and Mertens are all on 10-match winning streaks at Tour level, with Kerber's tally rising to 14 including Hopman Cup. Mertens is also on a 15-match winning streak in main draws on Australian soil.
Three of this year's semifinalists are current or former No.1s. The last time this happened at a major was at Roland Garros in 2013, when Serena Williams, Victoria Azarenka and Maria Sharapova were all part of the final four (along with Sara Errani). If Simona Halep loses her semifinal and Caroline Wozniacki wins hers, the top spot will pass to the Dane; if they both make the final, the winner will emerge as No.1.
This is the third time in the past four Slams that at least three of the semifinalists have never previously won a major. At Roland Garros, all four - Jelena Ostapenko, Timea Bacsinszky, Simona Halep and Karolina Pliskova - were going for their maiden Slam; at the US Open, CoCo Vandeweghe, Madison Keys and Sloane Stephens would do the same. Here, Simona Halep, Elise Mertens and Caroline Wozniacki are all hoping to emerge with their first major trophy.
This is also the third time in the past five years that three of the Australian Open semifinalists have never previously triumphed in Melbourne. It follows the 2014 lineup (Eugenie Bouchard, Li Na, Dominika Cibulkova and Agnieszka Radwanska) and 2016, which featured Radwanska again, Angelique Kerber and Johanna Konta.
None of the Australian Open semifinalists survived the second round at the previous major. At the US Open last year, Simona Halep, Angelique Kerber and Elise Mertens all lost in the first round (to Maria Sharapova, Naomi Osaka and Madison Keys respectively). Only Caroline Wozniacki won a match, falling in the second round to Ekaterina Makarova.
Elise Mertens is bidding to reach a Grand Slam final in just her fifth major appearance. Only five players have reached that stage quicker: Pam Shriver (in her second Slam, the 1978 US Open), Venus Williams (in her third Slam, the 1997 US Open), Chris Evert (in her fourth Slam, Roland Garros 1973), Natalia Zvereva (in her fourth Slam, Roland Garros 1988) and Monica Seles (who won her fourth Slam, Roland Garros 1990). Mertens, who is the first Belgian to reach a Slam semifinal since Kirsten Flipkens at Wimbledon 2013, would be the first Belgian in a major final since Kim Clijsters won the 2011 Australian Open.
This is Caroline Wozniacki's seventh Grand Slam semifinal - the most out of the remaining players. Previously at this stage, the Dane has won both semifinals in which she has faced unseeded opponents - Yanina Wickmayer at the 2009 US Open and Peng Shuai in Flushing Meadows five years later. However, she has lost every time she has played a seed: No.7 Vera Zvonareva at the 2010 US Open, No.9 Li Na at the 2011 Australian Open, No.28 Serena Williams at the 2011 US Open and No.2 Angelique Kerber at the 2016 US Open.
Angelique Kerber is in her sixth Grand Slam semifinal. Having lost her first two (to Samantha Stosur at the 2011 US Open and Agnieszka Radwanska at Wimbledon 2012), this was another statistic the German turned around in her career year to date of 2016 - defeating Johanna Konta at the Australian Open, Venus Williams at Wimbledon and Caroline Wozniacki at the US Open.
Simona Halep will play her fifth Grand Slam semifinal, and first at the Australian Open. The Romanian has won both of her matches at this stage at Roland Garros (over Andrea Petkovic in 2014 and Karolina Pliskova three years later), but lost both at other venues (to Eugenie Bouchard at Wimbledon 2014 and Flavia Pennetta at the 2015 US Open).
The last all-European semifinal lineup at the Australian Open was in 2012, when Victoria Azarenka beat Kim Clijsters and Maria Sharapova beat Petra Kvitova.
Elise Mertens has a 2-3 record against Top 10 players - but has won her last two matches and four sets over them, following her 7-6(4), 6-1 defeat of Dominika Cibulkova in Beijing last October with her 6-4, 6-0 victory over Elina Svitolina in the quarterfinals this week.
If Simona Halep and Caroline Wozniacki win their semifinals, they would set up the first Grand Slam final between No.1 and No.2 seeds since the 2015 Australian Open, when Serena Williams defeated Maria Sharapova. It would also be the first Australian Open final between two players without a major title to their name since 1980, when Hana Mandlikova beat Wendy Turnbull, and the first Grand Slam final in the Open Era featuring two players who had saved match point(s) en route. Halep fended of three against Lauren Davis in the third round, while Wozniacki survived two against Jana Fett in the second round.
Angelique Kerber's reputation is that of one of the strongest counterpunchers in the game - but following her quarterfinal rout of Madison Keys, Joel Drucker makes the case for the German as an offensive player at Tennis.com.
The reunion of Hsieh Su-Wei and Peng Shuai has paid off in the doubles competition - the two-time Slam champions are back in a major semifinal. They told to Xiang Bo for Xinhua that it's all down to their enduring friendship.
ORDER OF PLAY
The renaissance of 2016 Australian Open champion Angelique Kerber has been one of 2018's key narratives so far - and she's living up to the pressure as she's carved her way through the draw. Find out her thoughts after her quarterfinal win.