Kazakhstan end Germany's title defence in United Cup, US progress

Kazakhstan shattered Germany's title defence at the United Cup on Wednesday and secured their place in the semi-finals of the mixed team tennis tournament.

Elena Rybakina put Kazakhstan ahead with a comprehensive 6-3 6-1 victory over Laura Siegemund in the first match of the tournament's knockout stages.

Germany suffered a blow when world number Alexander Zverev withdrew from the quarter-final tie with a bicep strain minutes before his match.

His replacement Daniel Masur began well but Alexander Shevchenko prevailed 6-7(5) 6-2 6-2 to give Kazakhstan an unassailable 2-0 lead in the tie.

"It was a struggle in this heat. He made me run a lot, he was more aggressive," Shevchenko said after prevailing in a physical battle in Perth.

Shevchenko significantly cut down on his unforced errors after the first set and asserted himself more in a brilliant comeback.

Coco Gauff and Taylor Fritz won their respectively singles matches against their Chinese opponents to put the US in the last four.

Gauff downed an erratic Zhang Shuai 7-6(4) 6-2 to giver her team a perfect start.

The American looked under pressure in the opening set but found a way to get out of trouble before asserting herself.

Gauff made amends for her nine double faults in the match with 14 fewer unforced errors compared to her opponent's 40.

"I felt like, the hard I hit, the harder she was hitting," the 2023 US Open champion said.

"I felt like I couldn't get her on defence. She was playing so aggressive..."

Fritz downed Zhang Zhizhen 6-4 6-4 to clinch the tie for them with the mixed doubles to spare.

Earlier, in Sydney, Iga Swiatek inspired Poland to a 2-1 victory against Czech Republic in Group B that put them into the quarter-finals.

Tomas Machac put the Czech Republic ahead with his 7-5 3-6 6-4 victory against Hubert Hurkacz.

World number two Swiatek brought Poland level with a hard-fought 6-3 6-4 win against Karolina Muchova.

She returned to team up with Hurkacz to beat the Machac-Muchova pair 7-6(3) 6-3 in the deciding mixed doubles to secure their place in the last eight.

"Honestly I was sure they were going to play amazing tennis because they have always great teams in doubles and mixed doubles," Swiatek said.

"But I knew that we have the game to win it. For sure we were leading from the beginning," added Swiatek, who become the first player to secure 10 singles victory at the United Cup.