COCO Vandeweghe is the only unseeded player to have made it through to the quarter-finals of the women's singles, but Maria Sharapova will write the American off at her peril when the pair meet on Day Eight.

The world No 47, Vandeweghe has already disposed of two seeds - Sam Stosur in the third round and Lucie Safarova in the fourth - and although Sharapova will be the favourite, the Russian will need to be at her best to go through to the last four. Safarova, the No 6 seed, had her chances against Vandeweghe on No 3 Court on Day 7, but was knocked out 7-6, 7-6. The 23-year-old New Yorker held her nerve during those two tiebreakers, and if she remains as cool against Sharapova she will have a chance - even though she was less than impressed by her own performance.

"I didn't really feel that good," she said. "I thought it was one of my worst matches that I played the whole tournament so far.

"Serve was kind of in and out, but I think it was more my court positioning early on. I thought I was too far back, letting her dictate instead of making her feel my presence.

"But other than that, I kept calm and cool. When the tougher, longer rallies happened, I was on the winning end of it more times than I wasn't. I think that was kind of the difference in the match."

Sharapova herself, meanwhile, progressed to the last eight with a straight-sets win of her own, disposing of one of the other non-seeds, Zarina Diyas of Kazakhstan, 6-4, 6-4. Having been impressed by Vandeweghe's serve, the No 4 seed thinks her own return will be the key to victory.

In the bottom half of the draw, No 15 seed Timea Bacsinszky recovered from a poor start to beat the unseeded Monica Niculescu 1-6, 7-5, 6-2. The Swiss player now meets the No 20 seed from Spain, Garbine Muguruza, who knocked out No 5 seed Caroline Wozniacki 6-4, 6-4.

The quarter-final line-up will be completed by the meeting on No 1 Court of Madison Keys and Agnieszka Radwanska. Keys, the 21st seed, beat Olga Govortsova 3-6, 6-4, 6-1. Radwanska, the No 13, beat Jelena Jankovic 7-5, 6-4.