MADRID, Spain - Three-time Mutua Madrid Open champion Petra Kvitova won an eighth straight match at the Caja Magica, ousting 2017 runner-up Kristina Mladenovic, 6-3, 7-6(5) to reach the third round.

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"I think I'm trying to play well on all surfaces which I think is really showing and even today, it was a pretty difficult match," she said in her post-match press conference. "I fought hard in the end and that is what is counting. The clay and the conditions here are a bit different compared to other venues, so I always needed time to fight it out."

The defending champion navigated a tricky second set from the big-hitting Frenchwoman to clinch a tense tie-break after one hour and 55 minutes on Court Manolo Santana. 

"I'm glad I won the tie-break. That is my kind of issue sometimes, but overall it was pretty tight. In the first set I was up, I started pretty well and she came back, but then I took her serve again and it was a bit easier. In the second, I started very well as well but she just came back and played a bit better than the first set."

Since Kvitova fell to Mladenovic at the Open GDF Suez in Paris back in 2013, the two-time Wimbledon winner hadn't lost a set in their five successive meetings, including both of their 2018 clashes. Mladenovic, however, has shown signs of the form that took her to back-to-back finals at the Porsche Tennis Grand Prix and Mutua Madrid Open back in 2017 since pairing with new coach Sascha Bajin, who formerly worked with Serena Williams, Caroline Wozniacki and, most recently, World No.1 Naomi Osaka.

Breaking serve to start the match, the No.2 seed - though fresh off a win at the Porsche Tennis Grand Prix in Stuttgart - didn't have things all her own way on Monday as Mladenovic promptly broke back and forced two break points on the Czech's serve in hopes of taking the lead.

Kvitova dug deep to save both and ultimately captured the opening set with one more break of serve, serving it out with 11 winners to Mladenovic's four.

The second set followed a similar pattern as Kvitova broke first only for Mladenovic to catch up and play her higher-ranked opponent tough as she tried to force a deciding set, coming within two points of doing so at 5-4 and 6-5.

"Those two games when I was down 5-4 and 6-5 was very intense on my serve and I'm glad I didn't give her the chance, which was my strength, I think.

"In the tie-break it took a while to win the point on the serve! It was pretty tough. I think in the end of the tie-break, I'm pretty proud of myself that I kind of went for it and I hit a winner from the return and I played a backhand down the line as a winner and a great return in the end. So, I'm glad that I was able to go for it and playing positively."

Battling through the ensuing tie-break, Kvitova captured the final three points - smacking a blistering return at the Frenchwoman's feet - to secure her spot in the Round of 16, where either Romanian wildcard Sorana Cirstea or former World No.4 Caroline Garcia await.

"I think every round is tougher," she laughed when asked to name her biggest rival. "But I can't really say one name. I mean we are seeing a lot of new faces winning the tournaments for sure. On the clay, I think Simona Halep is a great one. Now, Naomi Osaka can play on all surfaces as well. I think Kiki Bertens is always very dangerous on the clay, so many of them I think, and my next opponent for sure as well!"