Perth (Australia), Dec 27 : Filling in for women's world No. 5 Zheng Qinwen, the world No. 175 Gao Xinyu caused a huge sensation, notching a major upset on the opening day of the United Cup, helping China to a 2-0 victory over Brazil in a Group E encounter.

Gao, who came in as a last-minute replacement for Zheng who decided to skip the United Cup to rest for the season ahead, overcame Beatriz Haddad Maia 5-7, 6-4, 7-5 to give China an initial 1-0 lead over Brazil in the opening rubber of the Group E tie.

The three-hour, 22-minute epic, which was the longest WTA singles match in tournament history, thoroughly contrasted Zhang Zhizhen's 6-3, 6-0 triumph over Thiago Monteiro, which sealed the tie in China's favour. Ranked No. 45 in the ATP Rankings, Zhang breezed past the Brazilian in just 54 minutes to improve to 2-0 in their ATP head-to-head series.

In Gao's show-stopping comeback, both players battled physical adversity. Gao required a medical time-out in the second set and resumed play with her left thigh heavily strapped, and the 27-year-old was in visible discomfort at times. Haddad Maia was afflicted by cramps when serving up 4-3 in the third set, resorting to several underarm deliveries and ultimately getting broken.

Nonetheless, both players put on a thriller for the RAC Arena crowd. No.175-ranked Gao, a replacement for Olympic gold medallist Zheng Qinwen, owned just one previous tour-level win in her career, and this was her first encounter with a Top 50 player. She had only notched one prior Top 100 win, all the way back in 2017 over Veronica Cepede Royg in Beijing qualifying that year.

But despite the gulf in experience, she went toe-to-toe with No.17-ranked Haddad Maia throughout and emerged with a career-best win.

Though Haddad Maia imposed her authority early with an immediate break, Gao settled into her groove and fired a trio of clean winners to break back and level at 5-5. She also held two points to force a tiebreak, but the Brazilian slammed down four consecutive unreturned serves to escape with a tight first set.

But Gao's tactics came to the fore in the second set as she pulled Haddad Maia off the court with sharp angles and used high forehands to reset points before picking her moments to strike. Still, as the match headed into a decider Haddad Maia seemed to have the physical advantage -- until cramps struck in a dramatic eighth game, according to a report on the event's official page.

Haddad Maia was able to move more freely by the next game, but Gao was in no mood to let her lifeline go. At 30-30 in the final game, she defied a net-rushing Haddad Maia with an excellent lob, then sealed victory as a Haddad Maia forehand sailed out. It was a fitting win for a player who hit the headlines last September for losing a 4-hour, 15-minute marathon against Sara Sorribes Tormo in Beijing, the fourth-longest WTA match of the Open Era.

/IANS