'I had a bit of a headache, my head was spinning': Heat floors star as United Cup finals take shape

Coco Gauff and Taylor Fritz powered the US, tournament winner two years ago, into the semi finals of the United Cup mixed teams tennis event on Wednesday.

In the first singles match, Gauff got the ball rolling for her team with a 7-6(4), 6-2 win over China's Zhang Shuai. Fritz then made sure of victory for the US by edging Zhang Zhizhen 6-4, 6-4.

“Shuai was playing amazing tennis out there. I was literally on the ground for most of the match,” world No.3 Guaff said.

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"The harder I hit, the harder she was hitting.

“I felt like I couldn’t get her on defence. She was playing so aggressive on me and I felt like I had to go more on my second serves, which brought in more double faults. But if I just put it in it was a return winner so I had to take my chances.”

The No.4-ranked Fritz said he didn't want to let Gauff down.

“There was a little bit of pressure because I didn’t want to be the one who loses it for the team after Coco won all her matches this week,” he said. "I played a really solid match. Really happy with it."

The Americans completed a 3-0 sweep when Desirae Krawczyk and Robert Galloway beat Zhang and Sun Fajing 6-3, 6-7 (1), 10-3 in the mixed doubles. The US next meets either Italy or Czechia.

Kazakhstan also advanced to the semi finals with a 2-1 win over a Germany team playing without the injured world No.2 Alexander Zverev.

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Zverev was a late scratch due to a biceps injury. He was scheduled to face Alexander Shevchenko but withdrew at the last minute with Kazakhstan leading the tie 1-0 after Elena Rybakina beat Laura Siegemund 6-3, 6-1.

Shevchenko beat Zverev's replacement, Daniel Masur, 6-7 (5), 6-2, 6-2 to clinch the tie while Zverev watched from the sidelines. Germany won the later mixed doubles.

Shevchenko took a medical timeout due to heat exhaustion while leading 1-0 in the second set. He came back from the break to dominate the rest of the match.

“It was a heat problem for sure,” Shevchenko said.

“I had a bit of a headache, my head was spinning. It was a struggle this match. To play in this heat was so tough."

Kazakhstan next meets Poland or Britain.

In Sydney, Iga Swiatek and Hubert Hurkacz won their deciding mixed doubles match over the Czech Republic to qualify Poland for the quarter finals.

World No.2 Swiatek and Hurkacz beat Tomáš Macháč and Karolína Muchová 7-6(3), 6-3 in the decider at Ken Rosewall Arena. The Polish team led 5-2 before allowing the Czechs back into the first set.

In earlier singles, Macháč gave the Czech Republic the lead with a 7-5, 3-6, 6-4 win over Hurkacz before Swiatek evened the tie with a 6-3, 6-4 win over Muchová.

In Sydney, Italy won Group D. Winners of the past two Davis Cups, and runners-up two years ago to the US in the inaugural edition of the season-opening mixed teams event, Italy won its group without world No.1 Jannik Sinner.

All tournament play shifts to Sydney from Thursday through to Sunday's final.