Pliskova, Halep, Muguruza, Stephens Into WTA Cincy Semis

Each woman would hold serve the rest of the way as Wozniacki did not make a dent in the Pliskova service game to close out the match.

The only one of four rivals who could have toppled Pliskova this week still with hope is second-ranked Halep, who ripped British seventh seed Johanna Konta 6-4, 7-6 (7/1) to book a semi-final date with United States wildcard Sloane Stephens.

"I think it was probably one of the best matches of the year", Muguruza said. "It was a battle". "I worked hard on beating these kinds of opponents". It was very tough. "He's too good a player for me to beat him at this stage".

Pliskova had 27 winners to Wozniacki's eight with only 13 unforced errors compared to the sixth-seeded Dane's 19.

Makarova let seven match-point opportunities slip away and saved one match point against her before the Russian completed a 6-4, 1-6, 7-6 (11) victory. Barty will face former world No. 1 Caroline Wozniacki, a 6-2, 6-4 victor against Russia's Elena Vesnina, in the last 16. Konta has won all three of their prior matchups.

Muguruza has needed two hours and 45 minutes - the longest of his three matches of the tournament - to ensure the victory.

Fifth-seeded Elina Svitolina of Ukraine defeated Lesia Tsurenko of Ukraine 6-1, 6-4.

These two have played three times and Muguruza has won two of those matches. "I worked a lot to give me another chance and here I am", Nadal said.

Before action got underway Friday at the Western and Southern Open, a moment of silence was observed in remembrance of the terrorist attack on Thursday that killed 14 in Barcelona.

Nadal was assured overtaking Britain's injured Andy Murray atop the rankings next week when Roger Federer withdrew Monday from Cincinnati with a back injury.Next for Nadal, who had a first-round bye, is a third- round matchup with 24th-ranked countryman Albert Ramos- Vinolas.

Stephens had earlier beaten Russia's Ekaterina Makarova 2-6 6-3 6-4. The Aussie double faulted on the last point to hand Karlovic the first set but forced an errant backhand to win the tie-breaker and dominated the last set. Bulgaria's 11th-ranked Grigor Dimitrov plays American John Isner in the other semifinal.

Czech Lucie Safarova will pass her injured U.S. partner, Bethanie Mattek-Sands, for world doubles number one on Monday after she and fill-in teammate Barbora Strycova advanced to the semi-finals.

  • Jo Lloyd