NEW HAVEN, CT, USA -- Three-time Connecticut Open champion Petra Kvitova of the Czech Republic moved into the quarterfinals in New Haven for the sixth time in her career after a 6-1, 5-7, 6-2 victory over qualifier Zarina Diyas of Kazakhstan.

"Probably something in the water, or in the air!" Kvitova exclaimed to the press about her superb record in New Haven, after the match. "The center court is probably a little bit faster than other courts. It’s a quiet place which I always love -- it’s a calm before the storm coming in New York, so it’s a great place to be. I just feel very comfy here, very relaxed, enjoying the time here."

No.3 seed Kvitova and Diyas had split their two previous meetings, but it was Kvitova who survived a nervy second set and a stern challenge from Diyas to take the rubber match in just under two hours, in their first-ever battle on hardcourt.

"Of course, I wanted to make it in two sets, but unfortunately, that happens sometimes," said Kvitova. She continued by saying that "luckily, I came back in the third one -- from the beginning [of the third set] I was there, and it was important to play each point."

Kvitova has played 21 three-set matches this season, winning 17 of them, more than anyone else on the WTA in 2018. "I’m just fighting in the third sets," explained Kvitova. "It’s about fighting in the third, I think. It’s just about a couple of points to win it."

"Of course at the end of the season you have a lot of three-setters, and I’m just glad that I do have a better percentage in them," Kvitova continued. "It’s not the first or last season like this, I’ve had so many three-setters before as well. I’m just kind of always putting so much effort in the third, I know it’s decided there."

Kvitova struggled with 42 unforced errors, including eight double faults, but her 35 winners well outweighed Diyas' 13. Kvitova also claimed 52 percent of points on both the first and the second serves of World No.62 Diyas, who this week played her first main draw since suffering a knee injury on grass at Nottingham in June.

Former World No.2 Kvitova, who re-entered the Top 5 on Monday for the first time since October of 2015, will take on Carla Suárez Navarro of Spain in the quarterfinals. Suárez Navarro moved into the final eight after her prospective opponent Johanna Konta withdrew before their match due to ilness.

Kvitova leads her head-to-head with Suárez Navarro 6-5, but the Spaniard has won four of their last five meetings. "I know how of a tough opponent she is," Kvitova admitted.

"[Suárez Navarro is] a very dangerous, very tricky opponent," Kvitova went on. "She can really mix it up, she always puts me in different positions. I never really know what’s coming from her side. We’ll see how everything will go, but I think it will be a great match, a nice one, fun to watch."

Two-time Wimbledon champion Kvitova got off to a flying start, blasting multiple forehand winners past Diyas to reach double break point at 2-1, then converting for the 3-1 lead with a service return winner.

Diyas was ready to strike back right away, using her speed and guile to reach double break point in the following game, but powerful groundstrokes from both wings of the Czech pulled her back to deuce, and Kvitova completed her comeback in that game with another winning forehand to hold for 4-1.

The story of the opening frame continued to be the powerful Kvitova forehand, as she used a running forehand, a rally-ending thumper, and a passing shot all from that side to reach break point for a 5-1 lead, which she converted by forcing an error with a sturdy backhand, for variety. A quick hold for 6-1 gave her the first set, in which she had a staggering 18 winners.

Diyas went down an early break in the second set, as Kvitova continued to hold the momentum. But the Kazakh methodically pulled her way back into the match, using angles and awkward placements to frustrate Kvitova into more errors. Diyas used her forehand to finally crack the Kvitova serve, tying the set at 2-2.

After a clutch of service breaks by both players, Kvitova served for the match at 5-4, though her fiery forehand had not been at its best throughout the second set. Indeed, the Czech could not successfully maneuver her way to that side, and dropped serve at love to let Diyas level at 5-5.

Diyas continued to move her replies to Kvitova around the court, fending off a break point at 5-5 with an error-forcing crosscourt backhand. After a hold by Diyas for 6-5, strong returns gave the Kazakh double set point on the Kvitova delivery in the next game. A solid serve by Kvitova saved one, but on the second, the third seed fired a backhand wide to hand the second set to Diyas.

Kvitova refused to be disheartened by the loss of the close second set, and reclaimed the ferocity on her forehand, blasting outrageous shots off of that wing on break points in the first and third games of the set to break Diyas both times and race to a 4-0 lead.

Diyas found the range on some marvelous forehands of her own as the set wore on, pressing Kvitova in each of her remaining service games. But the Czech denied any instance where Diyas could find inroads, and eventually used her vaunted serve and proficient power to coast through the rest of the set and claim a tough win.