Aleksandra Krunic of Serbia posted the biggest upset of the day at the Guangzhou Open as she ousted defending champion and fourth seed Lesia Tsurenko, 6-3, 6-4, in their opening-round match Monday. Krunic, who was winless against Tsurenko in four previous matches, will next face Mona Barthel of Germany, a straight-set winner over Jingjing Lu of China.

Third seed Anett Kontaveit of Estonia also reached the next round via an easy two-set win over Jasmine Paolini in just 69 minutes. Kontaveit, who never faced a break point against Paolini, will play the winner of the showdown between Lizette Cabrera and Xinyu Gao.

Eighth seed Alison Riske, for her part, lost in the first round to Rebecca Peterson, 6-3, 6-2. Other winners were Yanina Wickmayer, Kateryna Kozlova, Ipek Soylu and Danka Kovinic.

Sorana Cirstea hurdles opening-round assignment in Seoul

In South Korea, fourth seed Sorana Cirstea defeated Misa Eguchi in straight sets in the opening round of the KEB Hana Bank-Incheon Airport Korea Open. Cirstea dropped only four games and won 80 percent of her first serves as she ousted Eguchi in just 61 minutes. Cirstea will next take on either Nicole Gibbs or Korean wild card Jang Su Jeong. Fifth seed Irina-Camelia Begu overcame a tough challenge from qualifier Varatchaya Wongteanchai before escaping with a 2-6, 6-3, 6-3 triumph.

With the win, she advanced to the next round against Brazil’s Beatriz Haddad Maia, a 4-6, 6-3, 6-1 winner over Katarina Zavatska of the Ukraine 4-6, 6-3, 6-1. In other matches, Priscilla Hon defeated Karolina Muchova in three sets and Sara Sorribes Tormo ousted Heather Watson in three sets.

Kerber opens Toray Pan-Pacific Open campaign with win

Former world No. 1 Angelique Kerber started her Toray Pan-Pacific Open campaign in style, beating last year’s runner-up Naomi Osaka, 6-3, 6-4. With the win, Kerber avenged her loss to Osaka in the first round of the US Open. "It's really nice being back," said Kerber after the match, per

"It's always a great tournament and I always look forward to coming back to Tokyo and the Japanese fans.”

Kerber cruised to victory in the first set after she broke Osaka's serve, but the 19-year-old recovered in the second set, taking a 3-2 advantage with her accurate forehand. However, Kerber had less pressure from Osaka in the ensuing games as she cruised to a second-round showdown against the winner of the Madison Brengle-Daria Kasatkina clash. In other matches, eighth seed Kristina Mladenovic downed Qiang Wang of China in two sets while Kurumi Nara ousted Yulia Putintseva in three sets.