Anhelina Kalinina dealt out the biggest upset on Day 1 of the 2021 Kremlin Cup, knocking out former champion Daria Kasatkina 6-2, 6-3 in one hour and 23 minutes.

Russia's Kasatkina has historically excelled on her home indoor courts, first reaching the Moscow final in 2017 and capturing the title one year later. This year, she also added the St. Petersburg trophy to her haul. But the heavy-hitting Kalinina, who reached her first WTA final in Budapest this July and is currently at a career high of World No.57, dominated throughout their encounter, tallying 24 winners to 18 unforced errors.

Though Kasatkina had won the pair's only previous pro encounter 7-6(4), 6-1 in the first round of the 2015 Vancouver ITF W100 event, Kalinina did have a victory indoors to draw on from their junior days - in the semifinals of the 2013 Prerov Grade 1 tournament. Eight years later, she repeated it to defeat a second Top 30 opponent this year, following her triumph over Angelique Kerber in the first round of Roland Garros.

Keys to the match: The contest saw 12 breaks of serve in total. In both sets, Kalinina repeatedly powered ahead, but lapsed into nervy errors and a sprinkling of double faults when in the lead. But she was consistently able to steady herself on return. Kasatkina landed only 55% of her first serves, and Kalinina punished the second relentlessly.

The home player was also unable to get her offensive game clicking, conceding 22 unforced errors to 19 winners.

Turning point avoided: The quality of the match rose in the second set from both players, and the tensest moments came as Kasatkina attempted to mount a comeback from a double break down. The longest game of the match saw her narrow a 0-3 deficit to hold for 2-3 after five deuces and four break point saves.

But the World No.30 could not take advantage of winning that tussle, and missed two break points to level at 3-3 in the next game. Kalinina took control again, and despite two double faults preventing her from serving out the match, a drive volley ended matters on return.

Kalinskaya, Tsurenko make second round

Anna Kalinskaya, Lesia Tsurenko and Bernarda Pera all sustained their form from the qualifying rounds to win in the main draw. Tsurenko and Pera were both victorious in all-qualifier clashes, with Tsurenko besting the powerful Chinese 18-year-old Zheng Qinwen 6-4, 6-3 and Pera edging Aleksandra Krunic 7-6(3), 6-3 after needing six set points to close out the first set.

Kalinskaya, fresh off a career-best WTA 1000 performance after reaching the fourth round of Indian Wells, came from 3-5 down in the first set to oust Dayana Yastremska 7-6(5), 6-4. The Ukrainian produced some breathtaking examples of power tennis, but failed to find any consistency after losing her first-set lead.

Highlights: Pera d. Krunic

This was encapsulated in a wildly oscillating first-set tiebreak. Yastremska opened it with six straight unforced errors, hit her spots to save five set points (three with clean winners), but on the sixth pelted a return far outside the court.

Kalinskaya will next face No.3 seed Maria Sakkari, while Pera faces No.4 seed and 2014 champion Anastasia Pavlyuchenkova.