No.2 seed Simona Halep of Romania fought her way into the semifinals of Melbourne Summer Set 1 on Friday, outlasting No.6 seed Viktorija Golubic of Switzerland 6-2, 5-7, 6-4 at Melbourne Park. She was later joined by No.1 seed Naomi Osaka, who came from a break down in the second set to beat Andrea Petkovic 6-1, 7-5.

Halep served for the match in the second set before Golubic pushed the No.2 seed to the brink in a three-set tussle. However, Halep prevailed in a 2-hour and 35-minute barnburner to claim a spot in the last four.

Words from the winner: "It was really difficult, I have to admit," Halep said on court. "I didn’t really trust I could win this match, but I fought till the end. I’m very proud of this, because in the past I was working a lot on this way.

"[Golubic] played unbelievable, she was fighting till the end, all the credit to her for this beautiful match. I’m really happy that I could be a little bit stronger in the end. Winning this match means a lot."

Fast facts: Halep also needed three sets to take out Golubic in their only prior encounter, which the former World No.1 won at the Billie Jean King Cup in 2018. Golubic, who improved her ranking 94 spots last season and currently sits at World No.43, pushed Halep even harder this time around.

The first five games of the match went against serve, but Halep eventually won six games in a row to lead 6-2, 2-0. However, Golubic made a second-set charge, breaking Halep when the Romanian served for the match at 5-4. The Swiss suddenly went on a tear and won the final three games of the set.

In a close third set, Halep was in danger while serving at 3-4, where she had to stave off four break points. But Halep held on, then used a wicked rally slice backhand to force a Golubic error and break for 5-4.

Golubic's crafty game earned her two chances to once more level the set at 5-5, but Halep again fended off the break points, and closed out the encounter at last with a forehand winner.

Next up: Halep’s semifinal opponent will be rising teenager Zheng Qinwen. The 19-year-old qualifier from China is ranked World No.126 and contesting her fourth WTA main draw, and knocked out former Top 20 player Ana Konjuh of Croatia on Friday 7-6(1), 7-6(6).

Zheng had yet to reach a WTA quarterfinal prior to this week, but she beat former World No.2 Vera Zvonareva in the previous round to attain that accolade, and is now a round further after her 2-hour and 5-minute victory over Konjuh.

"Today I was happy with my performance," Zheng said after her latest victory. "I was 1-5 down in the second-set [tiebreak], and in that moment I said to myself, ‘OK, we’re going to go into a third set again, it’s OK!’ And since then, I started to play more free, and more relaxed, and that’s how I came back."

Read more: Five things to know about Zheng Qinwen

Looking forward to her match with Halep, Zheng said the two-time Grand Slam champion "is a really good player. When I was a junior, my father also talked about her to me, like that she is quite a fighter.

"I'm just going to give my best tomorrow, and I believe that I have the level to win, so I have to believe in myself. Don't look at the player as Simona, it doesn't matter. It's just what's open and in front of me, let's go ahead and try to get this match."

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Osaka delivers supreme performance to beat Petkovic

When Osaka opened the last quarterfinal of the day with three consecutive aces, it set the tone for a performance of frequently breathtaking quality from the top seed. The result took the defending Australian Open champion's winning streak in Melbourne to 13 matches (and 22 of her last 23 in the city stretching back to 2019).

The Japanese World No.13 did not let up during a near-flawless first set in which she tallied eight aces and dominated with easy power from the ground. But having broken Petkovic at the start of the second set, Osaka's supreme level dipped slightly, with her backhand going awry to hand the break back.

Interview: Petkovic relishing every moment: 'I'm seeing the finish line'

Improved serving from the German former Top 10 player saw her take advantage. Petkovic, who has said that "mentally, I'm at a really good place" as she embarks on what could be her final season, won four of five games to take a 4-2 lead.

During this passage of play, Osaka had still managed to come up with some superb shotmaking, including consecutive finesse winners in the fifth game - a reflexed half-volley and a delicate drop shot. With her back to the wall, she regained her baseline accuracy and her lethal first delivery.

Highlights: Osaka d. Petkovic | Q.Zheng d. Konjuh

Consecutive groundstroke winners saw Osaka break Petkovic back, and from this point she talled three more aces to take her match total to 11. At 5-5, Petkovic double faulted down break point, and Osaka nailed two backhand winners in a row to close out the win. In total, Osaka struck 33 winners to 15 unforced errors.

In the semifinals, Osaka will take on Veronika Kudermetova. For the second match in a row, the No.3 seed posted a three-set win that included a bagel set, this time overcoming Russian compatriot Anastasia Potapova 6-2, 4-6, 6-0.

Anisimova, Kasatkina book Melbourne 2 semifinal clash

Also on Friday at Melbourne Park, Amanda Anisimova of the United States became the first player into the Melbourne Summer Set 2 semifinals. Anisimova came back from a set down to overcome Irina-Camelia Begu of Romania 2-6, 6-3, 6-2.

Begu won the first five games of the match before 20-year-old Anisimova slowly pulled her way into contention. Anisimova eventually found a handful of pinpoint forehands at key moments to steer her way into her first WTA semifinal since 2020 Auckland, exactly two years ago.

Highlights: Anisimova d. Begu

No.3 seed Daria Kasatkina of Russia also made her way into the Melbourne Summer Set 2 final four on Friday. She defeated Nuria Parrizas Diaz of Spain 7-5, 6-1 in an hour and 38 minutes and will face Anisimova in the semifinals.

The bottom-half semifinal will pit American No.7 seed Ann Li against Belarusian qualifier Aliaksandra Sasnovich. Li, who has not dropped a set yet this week, continued her dominant form to defeat qualifier Kamilla Rakhimova 6-1, 7-5. Sasnovich advanced when No.6 seed Clara Tauson retired trailing 6-3, 2-0 due to a right thigh injury.