LONDON, Great Britain - Unseeded Slovenian Polona Hercog matched her career-best Wimbledon result with an upset of former quarterfinalist and No.17 seed Madison Keys in Wednesday's second round, 6-2, 6-4. 

Using a slice backhand and her athleticism to great effect, Hercog lured Keys into 31 unforced errors over little more than 70 minutes to reach the third round for the second time in the past three years.

After the pair traded breaks to begin the match, Hercog ran off seven consecutive games from a 2-1 deficit in the opener to lead by a set and a break.

The Slovenian never lost serve in the second set despite needing to save break points in a pair of service games. 

With the win, the World No.60 flipped the script of a straight sets defeat by Keys in May at the Internazionali BNL d'Italia, where she fell in a tight two-setter on her preferred surface of clay. 

Hercog has now reached the third round at back-to-back majors, and will next face15-year-old phenom Cori Gauff, whose history making run continued with a win over former semifinalist Magdalena Rybarikova, for a place in the second week. 

Read more: ‘My mindset improved, so my tennis changed’: Gauff passes Rybarikova test

"I was confused on who I played because I didn't actually look at the draw. I don't ever look. I just look at my next round," Gauff said.

"I don't know much. I'm going to look at some film tomorrow."

Including Keys, it was a mixed day for most seeds in the bottom half on Wednesday.

In other upsets, Australian Open semifinalist Danielle Collins came from a set down to beat No.12 seed Anastasija Sevastova, 3-6, 6-3, 6-4, despite nearly seeing a 4-0 lead disappear in the final set; while Dayana Yastremska edged No.27 seed Sofia Kenin in a high-quality clash of two rising stars, 7-5, 4-6, 6-3.

No.21 seed Anett Kontaveit, No.24 seed Petra Martic and No.28 seed Hsieh Su-wei were all winners, however.

Kontaveit eased past home favorite Heather Watson, 7-5, 6-1, while Hsieh edged former Wimbledon semifinalist Kirsten Flipkens, 7-6(3), 6-3.

"I'd say the first two games started well. That first set, I just felt like I had so many chances, but wasn't able to play aggressive tennis and get there. I sort of went on the back foot, just made too many errors," said Watson.

"After that first set, I don't feel that I changed a lot. I just feel like she relaxed and really stepped up her level, didn't give me a look in at all.

"I've played her a fair few times. I'd say returning is probably the biggest strength in her game. I knew that going in. I knew I'd have to serve well. In the second set I felt it was like first and second she was crunching.

"It was important for me to serve well today. I thought I definitely served better today than I did in my first round, but I feel like it was more my returns that let me down.

"I played a lot better than I have been. But I think that I hadn't played enough matches at this level, and it showed in the important moments today."