China's Zhu Lin lost to Belgian Elise Mertens 6-7 (8), 1-6 in the second round of the Australian Open on Thursday, marking the end of the road for all five Chinese in the women's singles draw. 

The 26-year-old Zhu had better luck in the women's doubles advancing to the next round with her Belgian partner Mona Barthel, as did the all-Chinese duo of Xu Yifan and Yang Zhaoxuan. 

Former doubles champions Zhang Shuai of China and Australian Samantha Stosur on Wednesday lost a three-set battle with Heather Watson and Leylah Annie Fernandez 6-4, 3-6, 6-2, dashing the chance to relive their 2019 victory. 

Also on Thursday, Sofia Kenin struggled to handle expectations in her maiden Grand Slam title defense while top seed Ashleigh Barty overcame a blip to reach the last 16. 

The fourth-seeded Kenin suffered a 6-3, 6-2 defeat in 64 minutes to the Estonian world No. 65, becoming the highest-ranked player to go out of the tournament. 

"I felt like I wasn't there, my head wasn't there," a teary-eyed Kenin admitted later. 

World No.1 Barty beat her Australian compatriot Daria Gavrilova in straight sets, but appeared to lose focus serving for the match before closing out for a 6-1, 7-6 (9/7) win against her Fed Cup teammate. 

Sixth seed Karolina Pliskova of the Czech Republic had few alarms in beating American Danielle Collins, a semifinalist at Melbourne Park two years ago, 7-5, 6-2. 

Swiss 12th seed Belinda Bencic was pushed harder by veteran Russian Svetlana Kutznetsova before coming through 7-5, 2-6, 6-4 in 2 hours 39 minutes. 

In the men's draw, Russian rising star Andrey Rublev, the seventh seed, reached the last 16 with a straight-sets victory over Brazil's Thiago Monteiro 6-4, 6-4, 7-6 (10/8). 

Rafael Nadal will test his sore back again as he chases a record 21st Grand Slam crown later Thursday. 

(With input from agencies)