MASON, Ohio -- Four-time Grand Slam champion Naomi Osaka was eliminated by Shuai Zhang, 6-4, 7-5, on Tuesday during the Western & Southern Open.
The tournament lost another big name, Coco Gauff, when she retired from her match against qualifier Marie Bouzkova with a left ankle injury. Gauff had her ankle taped after the first set and dropped out after the first game of the second set.
Karolina Pliskova advanced with a 7-5, 6-1 win over Williams' older sister, Venus. Bencic fell to Sorana Cirstea, 6-2, 6-7 (3), 6-4.
Rafael Nadal, sidelined since withdrawing from Wimbledon with an abdominal tear, practiced before a large crowd. The 22-time Grand Slam champion is scheduled to play a second-round match on Wednesday.
In a men's first-round match, Wimbledon finalist Nick Kyrgios beat Alejandro Davidovich Fokina 7-5, 6-4.