Tin-Tin Ho beat the world No 60 and second seed at WTT Feeder Otocec in Slovenia, while Connor Green also defeated a higher-ranked seeded player to reach the Round of 16.
Tom Jarvis also reached the last 16, while Green & Ho kept up their good run to reach the Mixed Doubles semi-finals.
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Having got past Katarina Strazar of the host nation in three straight in the Round of 64, Ho was up against Lea Rakovac of Croatia in the last 32.
Ho (WR 181) edged a tight first 11-9 and then led throughout the second, taking it 11-7.
The third saw Ho fight back from 6-2 down to level at 8-8 and from then on, both players traded chances to win the game. Ho saved five game points and missed two match points before Rakovac finally clinched the game 18-16.
When she then took the first three points of the fourth game, it look as if the momentum might shift, but Ho fought back and five points in a row to go 8-4 up put her back in charge and she went on to take the game and the match.
Her opponent in the last 16 will be Japanese 15th seed Kotomi Omoda (WR 131)
In the Men’s Singles, Green (WR 259) got through the first round with relative ease against lower-ranked Maxime Antoine Michard of France to set up a tie against Leonardo Iizuka (WR 122) of Brazil, the 10th seed.
Green twice led the match but was pegged back each time, missing out on two match points at 10-8 in the fourth, which Iizuka took 12-10.
But Green recovered from that disappointment to lead all the way in the decider, going 4-0 and 8-3 up and taking it 11-6 to set up a last-16 tie against Germany’s Kay Stumper (WR 107), the seventh seed.
Tom Jarvis (WR 68) had a bye into the last 32, where he defeated qualifier David Szantosi of Hungary, recovering a 2-1 deficit to win 3-2 – 11-8 in the decider. He next plays 14th seed Lin Yen-Chun (WR 146) of Chinese Taipei in the last 16.
Sam Walker (WR 221) was knocked out in the Round of 64 in five games by Mihai Bobocica of Italy (WR 206).
In the doubles competitions, WTT Feeder Dusseldorf champions Green & Ho kept up their good form as they won through two rounds against Slovenian and Indian opponents to reach the semi-finals.
Seeded second, they will face Brin Vovk Petrovski & Sara Tokic of the host nation in the last four.
In the Men’s Doubles, Green & Walker lost out in three to Japanese fourth seeds Kazuki Hamada & Kanta Tokuda in the first round.
Results
Men’s Singles
Round of 64
Connor Green bt Maxime Antoine Michard (FRA) 3-1 (11-8, 11-7, 4-11, 11-6)
Mihai Bobocica (ITA) bt Sam Walker 3-2 (14-12, 9-11, 11-8, 7-11, 11-4)
Round of 32
Tom Jarvis bt David Szantosi (HUN) 3-2 (11-6, 9-11, 8-11, 11-7, 11-8)
Green bt Leonardo Iizuka (BRA) 3-2 (11-9, 5-11, 11-7, 10-12, 11-6)
Women’s Singles
Round of 64
Tin-Tin Ho bt Katarina Strazar (SLO) 3-0 (11-6, 12-10, 11-3)
Round of 32
Ho bt Lea Rakovac (CRO) 3-1 (11-9, 11-7, 16-18, 11-7)
Men’s Doubles
Round of 16
Kazuki Hamada & Kanta Tokuda (JPN) bt Connor Green & Sam Walker 3-0 (13-11, 11-8, 11-5)
Mixed Doubles
Round of 16
Connor Green & Tin-Tin Ho bt Miha Podobnik & Katarina Strazar (SLO) 3-0 (11-5, 11-5, 13-11)
Quarter-finals
Green & Ho bt Riyan Dutta & Hardee Patel (IND) 3-1 (11-4, 8-11, 13-11, 11-5)