Second and third seeds Paula Badosa and Ons Jabeur eased into the Silicon Valley Classic quarter-finals on Wednesday, while Simona Halep and Jessica Pegula were bundled out of the Citi Open.

Last month's Wimbledon finalist Jabeur proved too good for American Madison Keys 7-5 6-1, winning in one hour and 22 minutes.

Jabeur, playing for the first time since Wimbledon, converted six of nine break points for the match, dominating the second set where she won 90.9 per cent first serve points.

Second seed Badosa survived a scare to win over qualifier Elizabeth Mandlik 6-2 5-7 7-6 (7-5) in two hours and 31 minutes.

Eighth seed Karolina Pliskova was knocked out by American Amanda Anisimova 3-6 7-5 6-1, while last year's runner-up Daria Kasatkina beat Taylor Townsend 6-4 6-0.

Two-time major winner Halep was forced to retire due to illness and top seed Jessica Pegula was bundled out by Daria Saville at the Citi Open.

In warm conditions, the 30-year-old Romanian battled throughout the match but eventually retired down 7-5 2-0 to Anna Kalinskaya after one hour and six minutes.

Halep had fought back from a 4-0 deficit in the first set to square it up at 5-5, before losing the first set.

However, the former world number one succumbed to illness early in the second set, handing Kalinskaya her passage into the quarter-finals.

On a dramatic day for the Citi Open favourites, world number seven Pegula was eliminated by Saville in straight sets in one hour and 38 minutes, 7-5 6-4.

Pegula was not helped by a first-serve percentage of 44.8 per cent, while she struggled to convert break points, with the Australian saving nine of 10 for the match.

Saville's win means she is 3-3 against top 20 opponents this year, progressing into the last eight where she will face Canadian qualifier Rebecca Marino.

Marino, who beat Venus Williams in her return to singles in the first round on Monday, knocked off Germany's Andrea Petkovic 6-3 3-6 6-1.

Estonian sixth seed Kaia Kanepi progressed into the quarters where she will face Kalinskaya after beating China's Zhu Lin 4-6 6-4 6-4.