DUBAI (AFP) - Aryna Sabalenka and Barbora Krejcikova, the top two seeds, both crashed to second-round defeats in the Dubai WTA tournament on Wednesday (Feb 16), with defending champion Garbine Muguruza also exiting on a day of upsets.

Belarusian Sabalenka, the world number two, fell 6-4, 6-4 to former Dubai winner Petra Kvitova. French Open champion Krejcikova lost 6-3, 7-6 (7/3) to qualifier Dayana Yastremska of Ukraine.

Russia's Veronika Kudermetova advanced to the quarter-finals past fourth seed Muguruza 3-6, 6-4, 6-4, with Latvia's Jelena Ostapenko edging out sixth seed Iga Swiatek 4-6, 6-1, 7-6 (7/4).

Tenth seed Elina Svitolina's hopes of adding a third Dubai title to her collection ended early at the hands of Swiss lucky loser Jil Teichmann, 7-6 (7/0), 6-2.

Kvitova, Dubai champion in 2013, took only 85 minutes to complete her third win in five meetings with Sabalenka.

The two-time Wimbledon champion's ranking has slipped to 25th, but the 31-year-old reached her first quarter-final of the season.

Kvitova next meets Ostapenko who got the better of her fellow former French Open champion Swiatek in a thrilling tie which included 16 breaks of serve and nine double faults for the winner.

Meanwhile, Teichmann's game was boosted by a solid serve which gave the 35th-ranked Swiss her second straight win over world number 15 Svitolina.

Teichmann next takes on Kudermetova who claimed her first win over Muguruza in four meetings in a match which lasted two hours and 17 minutes.

The Russian knocked out former world number one Victoria Azarenka in the first round on Tuesday.

The victory continues a solid start to the season for 24-year-old Kudermetova, who reached a WTA final in Melbourne, and the third round of the Australian Open in January.