TASHKENT, Uzbekistan – Nao Hibino stayed on course to defend her Tashkent Open title after Lesia Tsurenko retired from their quarterfinal on Thursday.

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Tsurenko arrived in Tashkent fresh from a run to the title in Guangzhou, and against Hibino this hectic schedule finally took its toll when a back injury brought her seven-match winning streak to a sudden end.

The anticlimactic conclusion to the contest was all the more disappointing given the competitive nature of the set they did play; after trading breaks, Hibino fended off two set points to take it 7-6(6). “I’m relieved after winning the first set. It was very close and I managed to hold on and fight in spite of being down,” Hibino said.

Standing between Hibino and another final in the Uzbekistani capital is World No.114 Denisa Allertova, a surprise 7-5, 6-4 winner over No.2 seed Kirsten Flipkens. Allertova produced the steadier tennis to edge the opening set, before claiming the decisive break in the final game of the match courtesy of a brilliant running passing shot.

In the top half of the draw, Kateryna Kozlova reached her second semifinal of the year after taking little over an hour to defeat Stefanie Voegele, 6-3, 6-3.

“I’ve played here before and made it to the quarterfinals last year, it’s great to play here,” Kozlova said. “I started to play aggressively from the word go and put my opponent under pressure early. I think I played brave and aggressive tennis, I’m happy with my level.”

Her reward is a meeting with big-serving Kristyna Pliskova, who fired down 12 aces during a 6-3, 6-4 win over Irina Khromacheva.