NANJING, China — Defending champion Viktor Axelsen advanced to the quarterfinals at the Badminton World Championships with a 21-19, 21-18 win over Angus Ng Ka Long of Hong Kong.

Axelsen was tested throughout the match as Ng jumped out to early leads in both games and kept it close.

“I didn’t feel that good on court, to be honest,” Axelsen said.

“My opponent definitely made it tough for me.”

The top -seeded Dane will next face Olympic champion Chen Long, whom he beat in the semifinals of last year’s world championships.

Chen beat No. 14-seeded Kenta Nishimoto 21-18, 21-19 to advance.

In women’s singles, No. 1-ranked Tai Tzu Ying of Taiwan defeated Zhang Beiwen of the United States 21-19, 21-14 to reach the quarterfinals.

Tai played a very strategic game, mixing up her shots beautifully to keep Zhang guessing the entire match. For Tai, it was just business as usual.

“Everyone has adapted to my play, I assume,” Tai said. “It has barely changed.”

Tai has looked unstoppable in 2018, with only one loss in 36 matches. Her lone defeat came against Thailand’s Ratchanok Intanon in the final of the Malaysia Masters in January.

Second-seeded Akane Yamaguchi of Japan eased past Thailand’s Nitchaon Jindapol in straight games to advance along with No. 5 Chen Yufei and No. 6 He Bingjiao of China.

In women’s doubles, top-seeded pair Chen Qingchen and Jia Yifan beat Du Yue and Li Yinhui 21-18, 21-13 in an all-China matchup. They will next face the No. 5 seed Greysia Polii and Apriyana Rahayu from Indonesia.

No.1-ranked mixed doubles pair Zheng Siwei and Huang Yaqiong beat Hafiz Faizal and Gloria Widjaja of Indonesia 21-15, 21-13 to reach the semifinals.