Cincinnati - Novak Djokovic battled stomach issues to beat Adrian Mannarino and reach the third round in Cincinnati on Wednesday as women's title holder Garbine Muguruza crashed out.
Wimbledon champion Djokovic called for the doctor during the second set against Mannarino but put aside his discomfort to progress 4-6, 6-2, 6-1 over the Frenchman before rain halted afternoon play.
"I wasn't feeling well, I didn't have a great night and wasn't feeling that well for the first set and a half," said Djokovic, who has won every Masters 1000 title except Cincinnati.
"I kind of made it through, and with the help of the doctor and God...I'm just, you know, happy that I managed to overcome the challenge.
"Credit to him playing well the first set, but I wasn't myself."
Seventh-seeded Muguruza played for the first time since crashing out in the second round of her Wimbledon title defence, falling 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 hardcourt build-up 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.
"I'm happy I didn't feel (arm) pain. Obviously I didn't have a lot of practices to try to recover, so I had to manage a little bit."
Marin Cilic, the 2016 men's champion, beat Romanian Marius Copil 6-7 (4/7), 6-4, 6-4, but third-seeded Alexander Zverev was upset 5-7, 6-4, 7-5 by Dutch veteran Robin Haase.
The German remains winless in four appearances at the pre-US Open tournament. His early exit comes a week after he lost in the Toronto quarter-finals to fellow youngster Stefanos Tsitsipas.
The 55th-ranked Haase clinched a surprise victory when Zverev fired a return long after losing serve six times.
"I think I played well. Today my returns I think were really, really good," Haase said.
"The first serve he hit at me was 136 (mph), and I just hit it right back. I was good from my side.
"Nowadays against top 10, 20, maybe top 50 you have to be a little bit lucky."
Zverev came into the event leading the ATP with 43 match wins this season, while it was a seventh career win over a top 10 player for Haase.
Wimbledon finalist Kevin Anderson of South Africa beat Jeremy Chardy 7-6 (8/6), 6-2 while Canadian Milos Raonic advanced over Malek Jaziri of Tunisia 6-3, 7-5.
Belgian 11th seed David Goffin eliminated France's Benoit Paire 5-7, 6-4, 6-2.
US Open women's champion Sloane Stephens was untroubled on her way into the third round, defeating German qualifier Tatjana Maria 6-3, 6-2.
The third-ranked American, who lost the Montreal final to world number one Simona Halep last weekend, reached the semi-finals here a year ago before falling to the Romanian.
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 beat Estonian Kaia Kanepi 7-5, 6-3, while recent Gstaad champion Alize Cornet was crushed 6-2, 6-0 by Ekaterina Makarova.
Results from the ATP and WTA Cincinnati Masters tournament on Wednesday (x denotes seeding):
Milos Raonic (CAN) bt Malek Jaziri (TUN) 6-3, 7-5
Novak Djokovic (SRB x10) bt Adrian Mannarino (FRA) 4-6, 6-2, 6-1
Grigor Dimitrov (BUL x5) bt Mischa Zverev (GER) 7-6 (7/5), 7-5
Robin Haase (NED) bt Alexander Zverev (GER x3) 5-7, 6-4, 7-5
Pablo Carreno-Busta (ESP x13) bt Bradley Klahn (USA) 6-4, 6-4
Karen Khachanov (RUS) bt Sam Querrey (USA) 7-5, 6-4
Marin Cilic (CRO x7) bt Marius Copil (ROU) 6-7 (4/7), 6-4, 6-4
Kevin Anderson (RSA x6) bt Jeremy Chardy (FRA) 7-6 (8/6), 6-2
David Goffin (BEL x11) bt Benoit Paire (FRA) 5-7, 6-4, 6-2
Nick Kyrgios (AUS x15) bt Borna Coric (CRO) 7-6 (7/1), 0-6, 6-3
Marton Fucsovics (HUN) bt Guillermo Garcia-Lopez (ESP) 6-7 (5/7), 6-4, 7-5
Stan Wawrinka (SUI) bt Kei Nishikori (JPN) 6-4, 6-4
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 Garbine 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 Karolina Plyskova (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