Emma Raducanu, of Britain, returns the ball to Ukraine's Marta Kostyuk at the Transylvania Open WTA tournament in Cluj, Romania on Oct 29, 2021. (RAED KRISHAN / AP)

Unseeded Chinese Wang Xinyu caused an upset at the Linz Open on Tuesday as she took out US Open champion Emma Raducanu 6-1 6-7(0) 7-5 in an absorbing three-setter to book her place in the quarter-finals of the WTA 250 event in Austria.

The defeat brought the curtain down on Raducanu's breakthrough season, during which she won her maiden Grand Slam, at Flushing Meadows in September.

With the match poised at 4-4 in the third, Emma Raducanu, seeking only her third win since her victory in New York, had to summon the trainer for what appeared to be an injury to her right leg

Wang, 20, got off to a blistering start and clinched the opener in just under half an hour as her deep returns forced the top seed into a number of errors. Raducanu was unable to match her opponent, who won over 85 percent of points on her first serve.

The 18-year-old Briton responded well in the second set, breaking in the first game following a rare error from Wang before the Chinese qualifier, ranked 106 in the world, hit back with a break of her own at 3-4.

Raducanu, however, outclassed Wang in the tie-breaker, striking a flurry of winners to win seven straight points and force a decider.

With the match poised at 4-4 in the third, Raducanu, seeking only her third win since her victory in New York, had to summon the trainer for what appeared to be an injury to her right leg.

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Despite the blow, Raducanu stayed in the contest by saving two match points at 4-5 but was eventually overpowered by Wang, who broke in the 11th game and comfortably closed out the match on serve when Raducanu sent a backhand long.

German tennis coach Torben Beltz, coach of Germany's Angelique Kerber, prepares to watch the women's singles final between US player Serena Williams and Germany's Angelique Kerber on the thirteenth day of the 2016 Wimbledon Championships at The All England Lawn Tennis Club in Wimbledon, southwest London, on July 9, 2016. Emma Raducanu of Britain has appointed Beltz as her new coach on Tuesday. (JUSTIN TALLIS / AFP)

New coach

Raducanu has appointed German Torben Beltz as her new coach, said the US Open champion after she was beaten in the opening match.

Raducanu had been without a coach since she parted ways with Andrew Richardson two weeks after her surprise triumph at Flushing Meadows in September, where she became the first qualifier to win a major.

He's (German Torben Beltz) obviously worked with Angelique Kerber who is such a great player and has done extremely well and won three Slams and I think that experience definitely helps with someone as inexperienced as me.

Emma Raducanu, British professional tennis player

"It's obviously a great privilege to be working with such an experienced coach. I'm definitely very excited to work with him throughout the pre-season and into next year," Raducanu, who had been the top seed in Linz, told reporters following the defeat by Wang.

"Very positive feeling about all the work there is to come."

Beltz, who recently split with compatriot Angelique Kerber, led the former world number one to the Australian Open and US Open titles in 2016.

READ MORE: Raducanu's search for new coach continues

"He's obviously worked with Kerber who is such a great player and has done extremely well and won three Slams and I think that experience definitely helps with someone as inexperienced as me..." added Raducanu.

"Also he's a really positive, cheerful guy who brings great energy to the team so I think that's also important when you're travelling on the road for quite a long time on the tour."

The 44-year-old also coached Croatia's Donna Vekic between 2017 and 2020, helping her break into the top 20 before rejoining Kerber's team last year.