US ninth seed Williams, seeking her third US Open crown, advanced to a Thursday matchup for a spot in Saturday's final against 83rd-ranked compatriot Sloane Stephens.
Maria Sharapova is expected to jump from 146th to around 100th in the world rankings.
Karolina Pliskova became the firm Wimbledon favourite on Wednesday when compatriot and two-time champion Petra Kvitova was knocked out.
Venus Williams wept at Wimbledon over the "devastation" of a fatal road accident for which she is facing legal action as Andy Murray and Rafael Nadal eased into the second round on Monday.
With the 23-time Major winner preparing for the birth of her first child and the Russian out with an injury, the race to the Venus Rosewater Dish is wide open.
The two-time Wimbledon champion swept aside American Julia Boserup 6-3, 6-2 in her first match of the French Open.
Petra Kvitova will make a "last-minute decision" whether to compete in the French Open as she prepares a comeback five months after her playing hand was badly injured in a knife attack.
The twice Wimbledon champion's left hand was badly injured in a knife attack at her home in December last year.
Petra Kvitova had surgery on December 20 following injuries on her left hand in the attack at her home in the town of Prostejov the same day.
Petra Kvitova suffered severe injuries to her racquet hand as she fought off a knife-wielding intruder at her home in the eastern Czech town of Prostejov on Tuesday.
Petra Kvitova suffered an injury on all five fingers and two nerves in her left hand, her racket hand, after fighting with the burglar at her home in the eastern Czech town of Prostejov.
Petra Kvitova, the Wimbledon champion in 2011 and 2014, is also recovering from a fatigue fracture on her foot which has ruled her out of the Hopman Cup starting on January 1.
Karolina Pliskova beat Kristina Mladenovic 6-3, 4-6, 16-14 in an epic rubber which lasted 12 minutes short of four hours as the Czechs, chasing a fifth title in six years, got off to a sensational start.
Top seed Novak Djokovic brushed aside Kyle Edmund in straight sets to storm into quarters of 2016 US Open. In women's singles, second seed Angelique Kerber reached the last eight after defeating Petra Kvitova
Seventh seeded Italian Roberta Vinci, defeated by compatriot Flavia Pennetta in last year's final, eased past Christina McHale of the United States 6-1, 6-3.
Rafael Nadal, a nine-time champion at the French Open, pulled out of the lone clay court Major with a wrist injury as reigning Olympic champion Andy Murray cruised into the Round of 16.
Defending Champion Stan Wawrinka, fifth seed Kei Nishikori, second seed Agnieszka Radwanska and two-time Wimbledon champion Petra Kvitova advanced to the French Open third round
Nick Kyrgios beat Italy's Marco Cecchinato in straight sets while Petra Kvitova survived scare to beat Danka Kovinic of Montenegro in first round matches of the French Open on Sunday