Rafael Nadal and Karolina Pliskova, the No 1 seeds at the Cincinnati Masters, never got a chance to break a sweat before play was halted Thursday at the rain-hit tournament.

Czech defending champion Pliskova led Italian qualifier Camila Giorgi 3-0 when play was suspended while former and future world No. 1 Nadal and compatriot Albert Ramos-Vinolas never started their third-round match before the final drenching began.

Court conditions more suitable for Olympic swim star Michael Phelps than tennis stars had US 14th seed John Isner, who beat teen Frances Tiafoe 7-6(4), 7-5, happy he snuck in a win between storms.

“Very happy to be off the court,” he said. “We could have easily, if I didn’t break at five-all, we could be two-all in a tie-breaker right now, not finishing. That would suck.”

Second-ranked Simona Halep of Romania charged closer to taking the world No 1 ranking from Pliskova by beating Latvian 15th seed Anastasija Sevastova 6-4, 6-3 to reach the quarter-finals.

“I’m not playing my best tennis in this moment but I’m still winning,” Halep said. “I win against the 15th player in the world playing not like I want and I’m really happy about it.”

But five matches were pushed to Friday, when double duty could come for Nadal, the 15-time Grand Slam champion assured of returning to world number one next week.

Nadal was assured of advancing past injured Andy Murray for the top spot when Roger Federer withdrew from Cincinnati with a back injury.

The 31-year-old Spaniard could meet Australian Nick Kyrgios in Friday’s quarter-finals. Croatia’s Ivo Karlovic led Kyrgios 4-3 in their halted match.

Nadal will be asked to play at 1 pm and again at 9 pm if he wins, as will the Karlovic-Kyrgios winner.

Eighth-ranked Austrian Dominic Thiem, the only other seed remaining in Nadal’s half of the draw, edged France’s Adrian Mannarino 7-6(4), 7-6(3). He faces Spaniard David Ferrer in the quarter-finals.

Final tune-up for US Open

Halep, a French Open runner-up for the second time in June, can overtake Pliskova by winning the title in the final major tuneup for the US Open.

“To be No 1 in the world I think is a big thing,” Halep said. “If I deserve the place, for sure I will win it.”

Ukraine’s fourth-ranked Elina Svitolina, who won her fifth WTA title of the year last week in Toronto to reach a career-high fourth in the rankings, can also become number one on Monday if she wins the title.

But she must face Germany’s Julia Goerges in a postponed match, then play the winner of another postponed match between American Sloane Stephens and Russian Ekaterina Makarova in a Friday double on short rest.

British seventh seed Johanna Konta downed Slovakian 11th seed Dominika Cibulkova 6-3, 6-4, to move into the quarter-final path of Halep, who won her 15th career WTA title earlier this year at Madrid.

Also reaching the quarter-finals was Wimbledon champion Garbine Muguruza. The sixth-ranked Spaniard saved three match points in downing 17th-ranked American Madison Keys 6-4, 3-6, 7-6(3).

“You never knew who was going to win until the last point,” Muguruza said. “I had match points against me so it was really hard. I battled back and I’m glad things went my way.”

Muguruza has a last-eight date with eighth seed Svetlana Kuznetsova. The 32-year-old Russian, a two-time Grand Slam champion, eliminated Spain’s Carla Suarez Navarro 6-2, 6-4.