The two previous meetings between the players had both gone Wickmayer's way and when she raced to a 4-1 lead in the opening set, she looked well poised for win number three. Dellacqua, however, had other ideas, reeling off seven unanswered games to take the opener and flip the match on its head.
The second set followed a similar pattern, Dellacqua breaking twice in the final four games to wrap up a 64 63 win. Meeting her in the last eight will be the in-form Aleksandra Wozniak, who defeated fellow Canadian Eugenie Bouchard, 62 62.
The other quarterfinal in the bottom half of the draw pits Jelena Jankovic against Sorana Cirstea. After coming through testing openers, both players enjoyed more routine outings in the second round, No.2 seed Jankovic seeing off Arantxa Rus, 76(5) 62, and Cirstea defeating Alizé Cornet, 61 75.
"She played well and it was tight in the second, so I'm really happy I could get through in straight sets tonight," Cirstea said. "I've been improving my play week to week and I'm feeling good about my chances here and ahead of the US Open."
Also through in straight sets was No.3 seed Roberta Vinci. Over the past few months the Italian has quietly gone about playing herself into form and taking on Polona Hercog impressed once again, posting a quick-fire 62 63 win.
"It was very hot and humid out there, but I played a good game," Vinci said. "I was focused, consistent, mixed up my play with a lot of slice and some serve and volley and I'm very happy with this match.
"I played well and really aggressive in Montréal and Cincinnati and I've continued that here. I like to play on hard courts. I play a lot of slice and that works well on fast courts like here. I won both matches easily so, for sure, I'm confident."
Next up for Vinci is Chanelle Scheepers, while the final quarterfinal will see Peng Shuai take on Bojana Jovanovski after they scored straight set wins over Pauline Parmentier and Mirjana Lucic, respectively.