Seeded players met little surprise en route to women's singles second round of the China Open in Beijing on Sunday, with 14th-seeded host player Wang Qiang an exception pulling out due to calf cramp, and her fellow Chinese Zhang Shuai bowed out in full sets.

Wang heated up quick into her opener against Ajla Tomljanovic to move ahead at 5-1, but her Australian opponent showed no concession to level the score at 5-all. Then Wang regrouped to take away the following two games for 7-5.

Procession of the second set was similar, as Wang started in style for a 4-0 lead, before Tomljanovic bounced back and only trailed at 4-5 after the ninth game.

Unable to hold on due to sudden cramp in her calf, Wang was forced to retire, sending Tomljanovic into the second round.

Japanese ace Naomi Osaka overcame Jessica Pegula of the United States 6-3, 7-6 (5).

Osaka, ranked world No. 4 and listed as the fourth seed, enjoyed a good start in the first set with more breaks than her opponent.

In the next set, Osaka suffered 19 unforced errors but Pegula failed to convert her chance. Osaka won the tiebreak 7-5 after coming back from losing four consecutive points to seal the victory.

"I was very nervous today. She kind of played much better in the second set. That was something that I had to get used to," commented Osaka.

Recovering from a back problem forcing her to retire from the Wuhan Open, sixth-seeded Simona Halep of Romania whitewashed Sweden's Rebecca Peterson 6-1, 6-1.

"I'm not 100% recovered. I still feel pain," admitted Halep. "But today I was very relaxed. I think I played smart. I played what she doesn't like."

The 13th-seeded Sloane Stephens got past Poland's Magda Linette 7-5, 6-3, setting up a second round clash with China's Zheng Saisai.

No. 10 seed Angelique Kerber from Germany broke twice early on to establish a 4-0 lead against Zhang, who won the next two games, but failed to continue her momentum afterwards. Kerber registered the third break of the match and went on to triumph in the first set 6-2.

The 31st-ranked Zhang took on a 6-1 victory to force a decider, where she once built a 4-2 lead. However, Kerber bounced back and won four games in a row to seal the deal.

"Today at the opening stage, I wasn't feeling great. I was trying to play more aggressively to raise my form, and felt improvement in the middle of the match. At the end of the match, I wasn't able to take key points, so I lost the match," Zhang pointed out.

Currently enjoying a career-best 48th place, China's Wang Yafan conquered her compatriot Wang Xinyu 6-1, 6-2 in less than one hour.

After both players held serves in the opening two games, Wang Yafan stormed to a 6-1 win in the first set.

On her maiden appearance in senior matches of the tournament, the 18-year-old Wang Xinyu slid away in her service early in the second set after seeing several deuces between the duo. Wang Yafan didn't give her compatriot many chances of coming back into contention before securing a spot in last 32 at 6-2.

In the second round, she will take on Ukraine's Elina Svitolina, as the third seed rallied past Anastasija Sevastova of Latvia 6-7 (4), 6-1, 6-2.

Despite featuring no seeded player, the encounter between American great Venus Williams and Wimbledon semifinalist Barbora Strycova caught huge attention.

Seven-time Grand Slam winner Williams triumphed 6-3, 4-6, 7-5 after more than two and a half hours.

"She's a great competitor. I was just super happy to win that at the end and stay in the tournament," Williams noted.