Britain's Sonay Kartal secured another huge win as she continued her impressive comeback from long-term injury at the Wuhan Open.
The 24-year-old made a flying start against world No 12 and former Olympic champion Belinda Bencic in the second round in China, going on to claim a 6-0 7-5 victory.
Kartal missed six months of the season with a stress fracture in her back, returning last month at the Billie Jean King Cup Finals in Shenzhen before reaching the third round in Beijing last week.
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Bencic is the highest-ranked player she has beaten since then world No 5 Mirra Andreeva in the Chinese capital last year.
Kartal, who plays Jasmine Paolini next, told a press conference: "I trusted that I would be able to get my level back, I just didn't know how quickly. I did a lot of things right today but I still think there's a long way to go.
"I can produce the level, but can I sustain it? I think that's going to be the hardest challenge. I'm happy to be back, I'm feeling good."
'I think I saw snippets from my tennis six months ago'
Kartal swept through the opening set before Bencic, who was a Wimbledon semi-finalist last year, responded at the start of the second, taking a 3-1 lead.
Kartal battled back and secured the crucial break at 5-5.
"Super high level from me right from the start," added the British player. "A match like that it's always tough to keep the scoreboard pressure when you've come out firing.
"Very happy with how I played in that match, the composure. I think I saw snippets from my tennis six months ago."
Kartal is ranked down at 170 following her injury break but is already guaranteed to leap around 40 spots.
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Swiatek beats fellow Pole Frech
Seventh seed Iga Swiatek eased into the third round with a 6-2 6-1 victory over fellow Pole Magdalena Frech.
Swiatek dropped her serve in the opening game of the match but then reeled off 10 games in a row to take complete control.
Frech stopped the rot with a break of serve to get back to 1-4 before Swiatek completed the win moments later in an hour and 44 minutes.
Swiatek said: "I'm happy to get the first match on the centre court because I didn't get a chance to play there before.
"At the beginning of the match, it was point by point, but then I was happy that I started making less mistakes and I used my chances until the end of the match. For sure it was tougher than the score."
Elsewhere, Karolina Muchova came from 6-3 2-0 down to defeat qualifier Caty McNally 3-6 7-6 (7-1) 7-6 (7-4).
Stream tennis with no contract on NOW and through the Sky Sports App. You can watch the WTA Wuhan Open and ATP Shanghai Masters live on Sky Sports, with those events running until Sunday.