Aryna Sabalenka still unbeaten in Wuhan, Beijing champ Coco Gauff cruises in opener

Second-ranked Aryna Sabalenka maintained her undefeated record at the Wuhan Open, opening her campaign with a 6-4, 6-4 win over 37th-ranked Katerina Siniakova in a second-round match on Wednesday.

Two-time defending champion Sabalenka, who received a bye in the first round with the other top eight seeds, broke her Czech opponent twice in each set—as well as surrendering one of her own service games—as she clinched her latest win in 1 hour and 34 minutes of play.

In the third round, the 26-year-old Belarussian will play Yulia Putintseva of Kazakhstan, who ended Paris Olympics silver medalist Donna Vekic's tournament with 6-4, 3-6, 6-4 victory.

Read More: Aryna Sabalenka welcomed back to Wuhan like an “old friend” as she eyes year-end No. 1 ranking

The reigning US Open champion is now up to 13-0 in Wuhan after winning the title on her first appearance in 2018 and defending her crown in 2019 before the tournament took its five-year hiatus from the calendar due to COVID-19 travel restrictions and a WTA boycott of China.

"I missed Wuhan a lot," Sabalenka said. "I just have really good memories of winning, two times, the title here. Just Wuhan brings me a lot of great memories, good vibes."

Sabalenka needs only to make the quarterfinals at Wuhan to regain top spot in the rankings from Iga Swiatek, who withdrew from the women's Asian swing citing fatigue and personal reasons. Swiatek recently split with coach Tomasz Wiktorowski.

There were six Americans in second round matches on Wednesday.

China Open champion Coco Gauff routed Bulgaria's Viktoriya Tomova 6-1, 6-2 in 75 minutes, while Hailey Baptiste upset 10th-ranked Barbora Krejcikova 6-3, 7-5 for her first win over a Top-10 player.

Read More: Magdalena Frech battles past Emma Navarro in Wuhan for first Top 10 win of career

Magdalena Frech beat eighth-ranked Emma Navarro 6-4, 3-6, 6-3 in just over two hours, and No. 11-ranked Daria Kasatkina overcame a mid-match stumble to defeat Amercian Bernarda Pera 6-4, 1-6, 6-1.

Amanda Anisimova withdrew from her match against 17th-ranked Marta Kostyuk.

Later Wednesday, third-ranked Jessica Pegula plays Anastasia Potapova and the Andreeva sisters—Mirra and Erika—face each other for the first time at a tour-level tournament.

Jannik Sinner avenged his defeat to Ben Shelton in the fourth round of last year's Shanghai Masters with a 6-4, 7-6 (1) to spoil the 22-year-old American's birthday on Wednesday.

Like last year, the duel again featured some incredible shot-making and serving dominance but this time the 23-year old Italian prevailed to improve his record against Shelton to 4-1.

"I think it was a very tough match also today," Sinner said. "He had chances in the first, chances in the second. If I don't play well these points, you know, he wins in two sets, because he was serving very, very well.

"Happy how I handled this situation, it's obviously a position where I have been last year, and where I am right now, it's different, so I'm happy to be in the position where I am."

Sinner's break in the ninth game was all that separated the duo in the opening set. Both players then dominated on their own serve through the second before the Italian sped away in the tiebreak and won the last seven points of the match.

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Sinner is now through to his seventh ATP Masters 1000 quarterfinal of the year and will play fifth-ranked Daniil Medvedev, who earlier beat long-time rival Stefanos Tsitsipas 7-6 (3), 6-3.

It was the 14th time the Russian former US Open champion and 12th-ranked Greek had met, but first in nearly a year. With Wednesday's win, Medvedex extended his head-to-head series lead to 10-4.

Second-ranked Carlos Alcaraz, who won the China Open in a thriller against Sinner last week, made it 12 consecutive wins with a testing 6-4, 7-5 victory over French veteran Gael Monfils to advance to the quarterfinals.

Alcaraz needed all his shot-making abilities to outmaneuvre the 38-year-old Monfils, with the 21-year-old Spaniard making 22 winners and taking a break in each set to clinch the match in 87 minutes.

"The main thing I tried in this match was to stay calm, to control my emotions and wait for my chances," Alcaraz said.

The French Open and Wimbledon champion will play Tomas Machac or Tommy Paul in the quarterfinals.

Later Wednesday, Novak Djokovic continues his bid for a 100th career title as he faces 61st-ranked Roman Safiullin.

Also, third-ranked Alexander Zverev plays David Goffin of Belgium and seventh-ranked Taylor Fritz plays Holger Rune of Denmark.