GSTAAD, Switzerland - No.2 seed Kiki Bertens navigated through a tight opening set before running away with a second round encounter with qualifier Anna Zaja, 6-4, 6-2, to reach the last eight at the Ladies Championship Gstaad.

Bertens took the only break of the first set, taking that momentum into the second to secure victory in one hour and 27 minutes.

“I’ve seen her in Nürnberg; she played great tennis there and plays well in general," Bertens explained after the match. "She serves well, and can be very aggressive. Of course here, it’s a bit tough. I think I managed to stay good in the match, get as many balls in the court.”

Bertens is back in Gstaad for a second straight year, finishing runner-up in 2016 after a stellar clay court season that saw her reach a maiden major semifinal at Roland Garros.

“It’s really nice. I enjoy being here. It’s a great hotel, and great site, around the mountains. I’m really happy to be here.”

Earning her career-high ranking of No.18 earlier this spring, Bertens brings a renewed sense of appreciation to the sport since dealing with a health scare for the better part of a year.

"It was tough because for one year, I didn’t know if it was good or bad. Finally, one year after, I heard that it was all good. After that, I could just focus on tennis again. I’m happy, healthy, and that’s the most important thing."

Bertens enjoyed a stellar serving day against Zaja, saving all four break points faced and winning 80% of points behind her first serve.

“It’s tough, but it’s tough for everyone. I don’t think anyone can play really good tennis and be aggressive in these conditions. You just have to go with it and know it’s the same for everyone.”

In the stands was doubles partner Johanna Larsson, whom Bertens will play for a spot in the singles semifinals.

“She was supporting me; I heard her shouting a couple of times. When we can, we try to support one another. It’s always tough to play one another, but we’ve only played once, so we’ve been lucky. It’s good that it’s in the quarterfinals and not in a first round, so I’m looking forward.”

Bertens and Larsson are top seeds in doubles and won their opening round match on Wednesday.

“It’s tough playing a good friend. We know each other so well. She’s alone here, and I’m with my coach, so he’s been helping her a bit. I’m glad one of us will be in the semis, and then we’ll play doubles after. During the match, it’s going to be tough, but after it’s going to be all good again.”

“I’m going for a title for sure, but I’m already happy to be in the quarterfinals. I’ll see what I can do; it’s going to be a tough match tomorrow against Johanna. At least one of us will be in the semis, so that’s good.”