The women’s draw took a beating on Wednesday in Cincinnati, where world number one Simona Halep’s was still battling when rain halted play.
The top-seeded Romanian stood 4-6, 6-3, 3-3 against Australian qualifier Ajla Tomljanovic when storms rolled in to bring the night session to an end on a day that had already seen one three-hour rain delay.
Halep had regained some momentum after falling two breaks down in the third set, with both women taking medical timeouts.
Halep was just one of the top women to run into trouble in the combined WTA and ATP Masters hardcourt tournament – the last major tuneup for the US Open.
Defending champion Garbine Muguruza, playing for the first time since losing in the second round of her Wimbledon title defense, fell 2-6, 6-4, 6-4 to Lesia Tsurenko.
“It was a very ugly match, but I’m happy that I fought, even if the level wasn’t very high,” said Muguruza, who got a late start to her buildup to the US Open because of an arm injury.
“At the end she managed to come back in the third set and play better and found a way to win the match,” said Muguruza, who was at least pleased to report that she played without any pain in her arm.
Second seed Caroline Wozniacki, however, retired with a left knee injury after surrendering the first set 6-4 to Kiki Bertens.
The Dane also lost her opening match a week ago in Montreal, following a second-round defeat at Wimbledon.
Wimbledon champion Angelique Kerber, the fourth seed, claimed her 40th win of the season, but she had to recover from a set down and needed two chances to serve for a 4-6, 7-5, 6-4 victory over Russian Anastasia Pavlyuchenkova.
“This was really a match where I was fighting after the first set to coming back,” Kerber said. “It was an important match to get my rhythm, feel the ball, especially now after few weeks off.”
US Open champion Sloane Stephens bucked the upset trend, winning easily into the third round 6-3, 6-2 over German qualifier Tatjana Maria.
Aryna Sabalenka of Belarus continued her successful tournament debut, beating ninth seed Karolina Pliskova 2-6, 6-3, 7-5. Australian 16th seed Ashleigh Barty defeated Estonian Kaia Kanepi 7-5, 6-3.
Ashleigh Barty (AUS x16) bt Kaia Kanepi (EST) 7-5, 6-3
Ekaterina Makarova (RUS) bt Alize Cornet (FRA) 6-2, 6-0
Lesia Tsurenko (UKR) bt Garbiñe Muguruza (ESP x7) 2-6, 6-4, 6-4
Angelique Kerber (GER x4) bt Anastasia Pavlyuchenkova (RUS) 4-6, 7-5, 6-4
Madison Keys (USA x13) bt Camila Giorgi (ITA) 6-2, 6-2
Aryna Sabalenka (BLR) bt Karolína Plíšková (CZE x9) 2-6, 6-3, 7-5
Elise Mertens (BEL x15) bt Rebecca Peterson (SWE) 3-6, 6-2, 7-6 (7/1)
Sloane Stephens (USA x3) bt Tatjana Maria (GER) 6-3, 6-2
Anett Kontaveit (EST) bt Maria Sakkari (GRE) 6-1, 6-3
Kiki Bertens (NED) bt Caroline Wozniacki (DEN x2) 6-4, retired