The top two seeds at the J&T Banka Ostrava Open both passed rigorous second-round tests to kick off their Czech campaigns.

No.1 Iga Swiatek handled the tricky challenge of Yulia Putintseva with poise, advancing to her fourth quarterfinal of the year 6-4, 6-4 in one hour and 47 minutes. She was followed on Center Court by No.2 Petra Kvitova, who was stretched all the way by qualifier Anastasia Potapova before winning 6-1, 6-7(4), 6-3 in two hours and five minutes.

Playing the second indoor WTA main draw of her career following Budapest 2019, where she reached the second round, Swiatek was given a tough workout by Putintseva, whom she was facing for the first time. The Kazakh was coming off a strong semifinal run in Portoroz last week, and her canny tactics and supreme defence provided a worthy foil to Swiatek's power.

Both players probing each other's games for weaknesses made for a number of absorbing, variety-filled exchanges in which every corner of the court was used. But although Putintseva's ability to mix spin, pace and direction tested Swiatek to the limit, the Pole remained positive and gradually got to grips with what she needed to do. By the second set, it was Swiatek who was increasingly emerging on top of even the longer rallies.

Match management: Putintseva had battled for three hours and 24 minutes to quell Zhang Shuai in the first round just 24 hours earlier, and was uncharacteristically errant as she swiftly fell behind 0-3. But once the 26-year-old found her groove and levelled at 3-3, almost every game was tightly contested.

It came down to Swiatek's ability to rise to the occasion at the tail end of each set, both of which she sealed with a break of her opponent's serve. She peaked with some dazzling all-court aggression to rattle off the last eight points of the first set, scoring winners at net and, on set point, off the return.

In the second, Swiatek showed her grit. Leading 3-2, she missed triple break point to break Putintseva; at 4-4, she had to fend off two against her, coming up with her fourth ace and a brace of brilliant backhand winners to do so. The final game saw Putintseva open the door with a pair of loose errors, and Swiatek needed no further encouragement. Two more backhand bangers in a row saw her edge over the line.

Quotable: "It was very tough," said Swiatek in her on-court interview. "She was running to every ball - it was really hard to finish her, especially with such a slow surface. She could reach everything and she was fighting to the end - even on match point I had to finish her, like, three times.

"I'm really happy I won, because normally it's really hard for me to play with such players. I like to risk and with risking comes unforced errors, so it's tough to get the balance between when to push and when to stay and wait for the opponent to miss."

Kvitova quells Potapova after procession becomes battle

After 50 minutes of play in front of her home crowd, Kvitova was enjoying a smooth procession into the last eight. She led Potapova 6-1, 4-2 and had dictated every aspect of the game to that juncture.

But the Czech crowd favourite would ultimately be stretched to the limit, needing to come from a break down in the deciding set to reach her sixth quarterfinal of 2021. Potapova had already showcased some superb hustle in the first round against Caroline Garcia, a match in which the 20-year-old conjured one of the shots of the year, and again demonstrated some otherworldly defence in turning her match against Kvitova around.

Stat corner: Potapova's numbers in the first set were unfortunate. The Russian tallied 14 unforced errors, including three double faults - all at inopportune moments - to only three winners. But over sets two and three, she would find 18 winners to 15 unforced errors.

By contrast, Kvitova kept a tight ship in the first set, with 10 winners to nine unforced errors. But as Potapova began extending points and testing her consistency, the next two saw 31 unforced errors come off the Kvitova racquet, with her forehand particularly letting her down in the closing stages of the second set.

Shot of the match: Potapova made her move as Kvitova served a 4-3 in the second set. She had been unable to take four previous break opportunities, but a return winner and stellar pass brought up triple break point in this game - and the World No.92 was determined to finally convert.

A booming forehand put Kvitova on the front foot, and the 31-year-old had Potapova at her mercy as she took on two short balls and two drive volleys. But Potapova scampered, hustled, flicked up desperate lobs, and finally managed to turn the point around with a wrong-footing backhand before finishing with a forehand flourish.

Match management: Having levelled at 4-4 with that shot, Potapova carried that energy through the ensuing tiebreak and into a 2-1 lead with the break in the third set. A second career Top 10 win was in sight.

But Kvitova blitzed a trio of breathtaking returns to break back immediately - and, serving at 3-4, the error-strewn Potapova of the first set returned at the most inopportune juncture. A slew of groundstroke errors put Kvitova in a position to serve for the win, and the World No.10 did so at her first opportunity. 

Ostapenko, Riske round out last 16

Earlier, last week's two finalists maintained their strong form in Ostrava. Jelena Ostapenko, runner-up in Luxembourg to Clara Tauson, bounced back to dominate lucky loser Anna Blinkova 6-4, 6-0 in just 66 minutes. The Latvian showed supreme proficiency in using the dropshot to exploit her opponent's movement, as well as her signature power.

Alison Riske had won just four matches throughout 2021 before last week, but doubled that tally to reach the Portoroz final before falling to Jasmine Paolini. The American came from 1-3 down in the third set before triumphing 6-4, 1-6, 6-4 over qualifier Fiona Ferro in two hours and 15 minutes.