Jil Teichmann of Switzerland picked up another quality win this summer by knocking out former World No.1 Angelique Kerber of Germany in the first round of the J&T Banka Ostrava Open on Tuesday.

In a battle between left-handers, World No.42 Teichmann notched her sixth win over a Top 20 player this season by ousting No.6 seed Kerber, 6-2, 6-3, in an hour and 12 minutes of play.

Half of Teichmann's six Top 20 wins this year came during her breakthrough run to the final at the WTA 1000 event in Cincinnati, where she beat Naomi Osaka, Belinda Bencic, and Karolina Pliskova before falling to World No.1 Ashleigh Barty.

In her first meeting against three-time Grand Slam champion Kerber, Teichmann took charge by winning 60 percent of points off the Kerber first serve, converting six of her nine break points on the day.

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Teichmann powered her way to a quick 5-0 lead in the opening set before Kerber made a brief comeback, holding for 5-1 and converting her fifth break point of the following game to reach 5-2. But deep, strong returns by Teichmann in the next game allowed her to break again for the one-set lead.

Three service breaks in a row left Teichmann holding a 3-1 lead in the second set, and she stopped that run of return dominance with a love hold for 4-1. Two double faults in the next game by Kerber ceded a love break and a 5-1 lead to the Swiss player.

But Teichmann could not serve out the match in that game, as a fiery crosscourt forehand by Kerber let the German claw one break back. However, that only delayed Teichmann's victory as she wrapped up the win two games later after a long return by Kerber.

Teichmann will now face either Alison Riske of the United States or French qualifier Fiona Ferro in the second round. Riske, last week's Portoroz runner-up, and Ferro will play their first-round match on Wednesday. 

Earlier on Tuesday, the Ostrava crowds were thrilled by a lengthy all-Czech, all-wildcard clash, where Tereza Martincova outlasted Katerina Siniakova, 5-7, 6-4, 7-6(7) to move into the second round.

The battle between World No.61 Martincova and 50th-ranked Siniakova took 3 hours and 6 minutes, with Martincova coming back from 0-5 down in the tiebreak, and saving one match point at 6-5 in that breaker.

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Martincova won four of the last five points to swipe the breaker and collect the win over her compatriot. It is Martincova's first main-draw win at the event, after losing to Barbora Krejcikova as a qualifier in the first round last year.

Astoundingly, a final-set tiebreak had also decided Martincova and Siniakova's lone previous meeting, which came at an ITF Challenger event in Nantes, France, in 2015. Siniakova, though, had won that particular encounter.

This time around, Martincova emerged the victor, but not without a struggle. Each player broke serve six times, but Martincova had many more chances than Siniakova, with 20 break points to Siniakova's 10.

Siniakova fired 49 winners to Martincova's 18, but Siniakova was undone by 67 unforced errors (including seven double faults), allowing Martincova to come back from a set down, an early break down in the third set, and 0-5 and match point down in the decisive tiebreak.

Martincova will now take on No.5 seed Anastasia Pavlyuchenkova of Russia, the 2021 Roland Garros finalist, in a second-round showdown. It will be their first meeting.