No.9 seed Petra Kvitova battled into her sixth career quarterfinal at the Mutua Madrid Open with a 6-3, 4-6, 6-4 win over Veronika Kudermetova, while No.8 seed Belinda Bencic moved into the last eight after a right thigh injury forced Ons Jabeur to retire trailing 7-6(2), 4-3.

"Definitely it was a tough one," said Kvitova afterwards. "It was about serving a lot. Was just the one break in each set. I'm really glad I managed most of it mentally. Veronika was really in the fire. Since she won Charleston, she really play great. She will be big champion.

"I would say whole match I was not relaxed, but calm I would say. That's how I managed to bring it to the win, I would say."

Kvitova has won in Madrid more times than any other woman, having lifted the trophy in 2011, 2015 and 2018. Her comfort in the Caja Magica was evident through a clean first set in which the Czech conceded only six points behind serve, and never faced a break point. After capturing the Kudermetova serve in the second game, Kvitova never looked like losing her lead.

Though Kvitova missed a break point to take a similarly early hold of the second set, the pattern continued. The two-time Wimbledon champion lost three points in her first four service games, while repeatedly putting Kudermetova under pressure. When Kvitova hammered her best winner of the match to reach double break point at 4-4, she seemed all but home and dry.

But Kudermetova has been getting used to winning in 2021. Her 22 match victories are second only to World No.1 Ashleigh Barty's 23, and her year was highlighted by a maiden title in Charleston last month. Kudermetova demonstrated her winning instincts with clutch serving to get out of that game.

Instead of serving for the match, Kvitova had to serve to stay in the set, and responded with her first loose service game of the day. Four forehand errors later, and the pair were suddenly in a third set.

Kudermetova, with the momentum for the first time, had the first break point chance to go up 2-0. But the Russian netted a backhand, and Kvitova took control again. A brilliant backhand return paved the way to a break in the next game.

The closing stretch wasn't all smooth sailing for Kvitova, who had to save two break-back points in the sixth game of the decider and come from 0-30 down to serve out the match. But she rose to the occasion both times, and after two hours and one minute sealed victory with her seventh ace. Next up will be a blockbuster quarterfinal against either Barty or No.14 seed Iga Swiatek.

Bencic's results on clay have yet to match her achievements on other surfaces, but the Swiss player tends to find her form in certain tournaments. Two of her four career clay quarterfinals have now come in Madrid, where she was a semifinalist in 2019. The other two were both in Charleston. Bencic ascribes this to the speed of the courts in these events.

"For sure I think Charleston it's the green clay, so it's little bit faster than the normal clay," she said. "Madrid, it feels of course like clay, but it feels a little bit more like indoor. The center court, it's very open. But the other courts, the one I played today and the one I played my first round, the roof is not so big - so it feels very indoor and very close. The court plays fast. It's a little bit of altitude here. It's good conditions. They suit me. It's for sure a faster clay than normally."

A high-quality first-time encounter between Bencic and Jabeur was unfortunately curtailed after the Tunisian pulled up while chasing down a forehand at 3-3 in the second set. After a medical timeout at the changeover, Jabeur resumed play, but two points later was unable to continue.

In a tight first set, Jabeur had impressed with some wonderful forehands, and had advanced to double set point on the Bencic serve at 5-4. But Bencic saved both with bold winners, and dominated the ensuing tiebreak with clean, aggressive play to take the lead. She will next face either wildcard Paula Badosa or qualifier Anastasija Sevastova.

"I felt terrible for her," said Bencic. "She's such a nice person. We are good friends. You never want this to happen to anyone. For sure I wish her the best recovery. But overall I thought we played a great match. There was no breaks at all in the whole match. I think her serving was great. I think it was a good level. I'm definitely happy with how I played and everything. But for sure I didn't want to win like this."

Kvitova squeezes past Kudermetova in 3 sets to reach Madrid QFs: Highlights

2021 Madrid