Lesia Tsurenko plays a backhand shot to Garbine Muguruza during the Cincinnati Masters at Lindner Family Tennis Center in Mason, Ohio. Image Credit: AFP

Ukraine’s Lesia Tsurenko stunned defending Cincinnati Masters champion Garbine Muguruza as the world’s top players faced difficulty during a rain-shortened second round.

Tsurenko took down the seventh-seeded Spaniard 2-6, 6-4, 6-4 in the early match, which was a preview of the challenges faced by top seeds during the day.

World number one Simona Halep fell down a set but rallied against Australia’s Ajla Tomljanovic, and was leading 4-6, 6-3, 4-3 when her match was suspended due to rain.

Second seed and Australian Open champion Caroline Wozniacki lasted just one set against Kiki Bertens before retiring due to a left knee injury.

The match was delayed by rain for over three hours and Wozniacki retired shortly after Bertens captured the opening set in 62 minutes.

“It’s never nice to win when someone has to retire,” Bertens said. “I felt she was struggling a bit with her serve. She seemed to struggle with her movement as well.” Fourth seed Angelique Kerber also had a difficult outing, having to battle back to outlast Anastasia Pavlyuchenkova 4-6, 7-5, 6-4.

Muguruza was competing in her first tune-up event for the US Open, having been sidelined due to an arm injury that forced her to withdraw from a pair of tournaments.

It was her first match since losing in the second round at Wimbledon.

“I’m happy that I didn’t feel pain,” she said. “I competed. It didn’t go my way. I’m going to take that positive and keep training for US Open.” Next up for Tsurenko is a clash with Ekaterina Makarova after the Russian topped Frenchwoman Alize Cornet 6-2, 6-0.

Joining Tsurenko in the third round was US Open champion Sloane Stephens, who enjoyed a routine 6-3, 6-2 win over German Tatjana Maria.

Stephens, who finished runner-up to Halep in Montreal on Sunday, continued her fine form on the North American hard courts and controlled the tempo throughout her 71-minute match.

Stephens will next face Elise Mertens after the 15th-seeded Belgian earned a 3-6, 6-2, 7-6 win over Swedish qualifier Rebecca Peterson.

On the men’s side, Dutchman Robin Haase upset German fourth seed Alexander Zverev 5-7, 6-5, 7-5 and Wimbledon winner Novak Djokovic cruised into the third round before rain interrupted play.

Haase, who last week kicked off his North American hard court swing by reaching the Toronto quarter-finals, converted six of seven break point opportunities to get by world No. 3 Zverev in a match lasting two hours and 25 minutes.

World No. 55 Haase improved to a 2-2 career record against Zverev, including victories in their last two meetings.

“We’ve played four times now,” Haase said. “The first time he literally kicked my butt ... That was the tournament where he actually came up. And, yeah, since then he’s come a long way.

“And now I was there twice physically, mentally and game-wise I was there. And we have to be a little bit lucky, as well, against these top guys.” Haase will face Pablo Carreno Busta in the third round after the Spanish 13th seed beat Bradley Klahn 6-4, 6-4.

Zverev’s older brother Mischa fell to defending Cincinnati champion Grigor Dimitrov 7-6, 7-5 in a match delayed by rain.

Djokovic, who needs the Cincinnati title to complete his collection of ATP World Tour Masters 1000 trophies, rallied to defeat Frenchman Adrian Mannarino 4-6 6-2, 6-1.

The 10th-seeded Serb, who has reached the final five times, suffered stomach problems during the match and was tended to by a doctor during the second set.

“I didn’t have a great night and wasn’t feeling that well for the first set and a half,” Djokovic said. “I kind of made it through, and with the help of the doctor and God, I’m just happy that I managed to overcome the challenge.” Djokovic returned to wrap up the second set and raced into a 5-0 lead in the decider before serving out the match. Djokovic will next face fifth seed Dimitrov.

Former champion Marin Cilic of Croatia beat Romanian qualifier Marius Copil 6-7, 6-4, 6-4.

Sixth seed Kevin Anderson overcame Jeremy Chardy 7-6, 6-2 while Swiss wild card Stan Wawrinka knocked out Japan’s Kei Nishikori 6-4, 6-4.