In Saturday's semifinals, del Potro will play doubles specialist Edouard Roger-Vasselin of France, who beat Daniel Brands of Germany 6-3, 4-6, 6-3.
Sania and her Chinese partner Jie Zheng lost to Australian pair of Ashleigh Barty and Casey Dellacqua 6-2 6-2 in the last-4 clash.
The Indo-Chinese pair will now take on 8th seeded Australian pair of Ashleigh Barty and Casey Dellacqua in the semi finals on Thursday.
Playing just their fourth event together, third seeds Sania and Jie pipped the second-seeded pair of Anabel Medina Garrigues and Katarina Srebotnik 6-3, 6-4 in the summit clash.
Sania Mirza, the only Indian female to win Grand Slam title, has won two titles so far this season. Both the titles came with American partner Bethanie Mattek-Sands, who now plays only singles.
Mauresmo said she had not seen the decision coming but that the pair had been in contact overnight, first by text message, then by telephone.
Williams next faces No.13 seed Kirsten Flipkens, who beat Dutch qualifier Kiki Bertens 7-5, 3-6, 6-2.
Flipkens leveled the match with a break in the 10th game of the second frame, and once the 13th-seeded Belgian had forced the third set it was Williams who couldn't keep pace.
Williams suffered her earliest French Open exit in 12 years in May, when she crashed to a first-round defeat to Poland's Urszula Radwanska.
Sania had played with American Lizel Huber at the Wimbledon where she made a third round exit.
Marion Bartoli blitzed the field at the All England Club to win her first Grand Slam title and will be making her second appearance at the mixed team tournament from December 29-January 4.
Sharapova and Flipkens will be replaced in the 28-player draw by world number 46 Daniela Hantuchova and Christina McHale, who is ranked 79th.
Scotland Yard said a 30-year-old man was arrested and bailed over the alleged attack on the 34-year-old woman.
Monfils had 16 aces to set up a meeting with sixth-seeded Florian Mayer, who defeated another German, Andreas Beck, 6-4, 3-6, 6-1.
As the 11-year-old girl lit up the Centre Court with her smile at the coin-tossing event, Lady Luck smiled on Andy Murray and more so on Britain, which ended its 77-year men's singles title drought.
The event, attended by celebrities like Naomi Campbell and Boris Becker, was for a social cause as part of the Novak Djokovic Foundation.
The 2013 Wimbledon winner reveals that Sears 'really understands tennis'.
Taiwan's tennis hero Su-Wei Hsieh is mulling giving up her Taiwanese citizenship to represent China, where she could receive a much bigger sponsorship deal her father said on Monday, after her historic victory in the Wimbledon women's doubles contest.