Karolina Muchova and Tomas Machac delivered a devastating 1-2 punch on an overmatched Italy Friday night to lead the Czech Republic into the semifinals of the United Cup in Sydney.

After World No.22 Muchova conceded just four games in her fifth consecutive win over World No.4 Jasmine Paolini, Machac imposed his physicality on 22-year-old Flavio Cobolli to clinch the tie.

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"I really wanted to bring a point to the team so I was trying to stay focused," Muchova said after her 6-2, 6-2 win. "Jasmine is an unbelievable player. It was a really tough match. I knew I had to go until the end. She had many break chances. I think I served well. I'm really happy I made it."

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Once again, Muchova's attacking game proved too much for Paolini, who has won just one set in the pair's five meetings. Their last duel came at the US Open last fall, where Muchova prevailed 6-3, 6-1 en route to the semifinals. 

The two went toe-to-toe for the first four games of the match before Muchova broke it open for good. Ranked No.22 on the PIF WTA Rankings, Muchova maintained consistent return pressure on Paolini, who struggled to get enough lift on her forehand to bother the Czech.

"I have to find another way to play against her, of course," Paolini said, "and I have in my mind, but for the next one hopefully. Hopefully it's going to be better. But she's playing unbelievable."

Muchova broke first by winning the longest game of the match, converting on her fifth break point. She maintained control from there, losing just two games for the remainder of the match. Muchova enjoyed a perfect serving day, saving all 10 break points she faced.  

Entering the season at a career-high No.25 in the PIF ATP Rankings, 24-year-old Machac breezed through service games and outmuscled the World No.32 from the baseline. He charged through the first set in just 23 minutes and claimed a 6-1, 6-2win in just 54 minutes.

"I think this is the highest level of tennis that I can play," Machac said. "I'm really happy to play like this in such an important moment. I was surprised how I played great without any mistakes and I didn't give him any opportunity to come back."

"I know I have this kind of level but to play and when I saw how the match was going I just tried to be strong mentally for as long as possible. I was playing like Novak!"

In group play, Machac pushed World No.6 Casper Ruud for nearly three hours and upset World No.14 Hubert Hurkacz.

This time last year Machac needed to qualify at the ATP 250 event in Brisbane to begin his season and did not own a win against a Top 10 opponent. But in a banner year he claimed 33 match wins and slashed his ranking from No.78 to No.25.