Coco Gauff lamented her "flat" performance after being dumped out of the China Open in the fourth round by Elise Mertens on Wednesday.

Mertens claimed a 6-3 6-3 victory over the third seed in Beijing, her first win over the American in six head-to-head meetings between the pair.

Three consecutive breaks – two at the end of the opening set and one at the start of the second – proved enough for Mertens, who served tremendously when the pressure was on to get over the line.

She won 10 of her last 11 points on serve – including a booming ace on her second match point – to tee up a quarter-final meeting with Iga Swiatek on Friday.

Gauff, meanwhile, produced an error-strewn display containing eight double faults and a first-serve rate of just 52% – she also won just 61% of her first-serve points (20/33). 

"I think I just didn't play well," Gauff said. "I think I wasn't moving well. There were a lot of things I didn't do well. 

"I thought Elise played well on the big points, made me play some big balls. I was just a bit flat. That's the main thing.

"The level was there on some points, I just didn't sustain it for the whole match."

Gauff had spoken out after receiving racist abuse on social media following her third-round victory over Sun Xinran on Monday, and she admitted the experience had affected her preparations.

"It has been kind of draining, I'm not going to lie," she said. "I just turn off my phone and move on. I mean, there's nothing you can do."

3 - Achieving the feat for the first time in her career, Elise Mertens is one of five players to claim WTA top 10 wins on all three surfaces in 2026 after Karolina Muchova, Linda Noskova, Emma Navarro and her defeated opponent, Coco Gauff. Adapt. #ChinaOpen | @ChinaOpen @WTA https://t.co/zlPTiHHXBE

— OptaAce (@OptaAce) October 7, 2026

Mertens' next opponent, Swiatek, swept Iva Jovic aside for a convincing 6-1 6-3 victory, advancing to her 31st career WTA 1000 quarter-final – among active players, only Aryna Sabalenka has reached more (33).

"I was more proactive, I was changing direction more, instead of just being solid – it was more intense," Swiatek said.

"When I needed to, I could play long rallies and play defensively, as well. Everything was working today."

Mertens ends five-year wait, Swiatek matches Serena

Mertens' upset of Gauff booked her first quarter-final appearance at a WTA 1000 event since Madrid 2021, when she lost to eventual champion Sabalenka.

Her previous WTA 1000 quarter-final on hard courts also came in 2021, and she also lost to the eventual champion in that instance, albeit reaching the last four before going down to Garbine Muguruza.

All of that may bode well for Swiatek, who has become just the second player, after Simona Halep, to reach at least six WTA 1000 quarter-finals in four different seasons, since the format's introduction in 2009.

And, with 148 victories at WTA 1000 events overall, Swiatek has gone joint-seventh in the all-time charts, alongside Serena Williams.