Rafael Nadal and Karolina Pliskova - the No 1 seeds in the Western & Southern Open — advanced with straight-set wins Wednesday, while the rest of their brackets suffered more top losses.
Nadal sat out an hour-long rain delay and beat Richard Gasquet 6-3, 6-4 on Wednesday night, finishing it off with two of his eight aces.
Pliskova needed only 67 minutes to get a 6-2, 6-3 win over Natalia Vikhlyantseva, a solid showing as the defending champion. She'd never faced the Russian and wasn't sure what to expect.
The rest of the hot, muggy day was highlighted by upsets.
Venus Williams' resurgent summer hit a bump when she was knocked out by a qualifier. Ashleigh Barty rallied for a 6-3, 2-6, 6-2 upset on a humid afternoon that played to her advantage.
Barty, ranked No 48 on the ATP tour, had never beaten a Top 10 player — going 0-6 — before knocking off the ninth-ranked Williams.
Williams is enjoying a comeback season, reaching the finals at the Australian Open and Wimbledon at age 37. She faded in the heat and humidity on Wednesday against a player who is 3-13 career against Top 20 players.
After knocking off Williams, Barty had to head for her doubles match, still buoyed by the biggest win of her singles career.
"It really is a privilege to be able to share the court with Venus," Barty said. "She's an amazing champion and how she's still playing so well, still making Slam Finals — it's amazing."
No 3 Angelique Kerber lost to Ekaterina Makarova 6-4, 1-6, 7-6 (11), with the Russian converting on her eighth match point to end a 2-hour, 39-minute match. Makarova also upset Kerber at Roland Garros this season.
Kerber fell behind 5-2 in the third set, rallied to a tiebreaker, then got up 8-7. She wasted her only chance to finish it off.
"The third set was a completely up-and-down set," Kerber said.
Makarova got cramps in both legs during the third set, and they got worse during the tiebreaker, forcing her to get treatment briefly.
The men's bracket lost one of the hottest player of late.
Wild-card Frances Tiafoe broke through against No 4 Alexander Zverev, who was coming off his second ATP Masters title in Montreal. The 19-year-old American hadn't taken a set in his two career matches against Zverev, but rallied for a 4-6, 6-3, 6-4 victory that ended Zverev's streak of 10 straight match wins.
Sania-Shuai advance
Indian tennis ace Sania Mirza and her Chinese partner Peng Shuai advanced to the quarter-finals of the Cincinnati Masters following a straight-set victory in the women's doubles clash here. The fourth seeded Indo-Chinese duo romped home with a comfortable 7-5 6-4 win over Germany's Julia Görges and Ukraine's Olga Savchuk in a last-16 clash that lasted one and a half hour on Wednesday.
Meanwhile, India's Ramkumar Ramanathan crashed out of the tournament after going down to American wild card Jared Donaldson in the second round men's singles tie.