Bojana Jovanovski continued to make hard work of her Tashkent Open defence in a 7-6 (8-6) 3-6 6-3 win over Alla Kudryavtseva on Wednesday.
The Serbian is looking to become the first woman to defend the WTA International hard court event in Uzbekistan, but has been far from convincing on her way to the quarter-finals.
Jovanovski overcame an early scare to beat Kateryna Bondarenko 1-6 6-4 6-1 in the first round, and took two and a half hours to get the better of 2010 champion Kudryavtseva.
After coming from a break down to win the opening set, Jovanovski won just half of points on her first serve in the second.
Just four games went with the serve as Kudryavtseva pulled level, before a third set which was just as unpredictable.
However, this time Jovanovski outnumbered her Russian opponent by three breaks to two to set up a last-eight meeting with Urszula Radwanska.
In contrast to Jovanovski, Radwanska has made relatively light work of her two matches so far.
After beating Vesna Dolonc 6-2 6-2 in round one, the Pole cruised past third seed and 2012 runner-up Donna Vekic 6-3 6-3 on Wednesday.
The biggest shock of the day came as second seed Irina-Camelia Begu was dumped out by Ukrainian qualifier Lesia Tsurenko - losing 3-6 6-1 7-6 (7-3).
She now faces Ksenia Pervak, who triumphed 6-2 7-6 (7-3) over Jelena Ostapenko.
Home fans will be relishing the chance to see an all-Uzbek quarter-final when Akgul Amanmuradova takes on Nigina Abduraimova.
Amanmuradova dismantled Lyudmyla Kichenok 6-1 6-2, while Abduraimova fought back to triumph 2-6 6-3 6-4 over Alexandra Panova.
Last year's beaten finalist Olga Govortsova of Belarus defeated sixth seed Misaki Doi 4-6 6-3 6-3 to book her place in the quarter-finals, where she will meet Italy's Karin Knapp - a 6-2 6-3 winner over Aliaksandra Sasnovich.