Last year's runner-up, Agnieszka Radwanska, moved into the semifinals, while 2011 champion Petra Kvitova joined the list of upset victims at Wimbledon.
The fourth-seeded Radwanska held off sixth-seeded Chinese star Li Na 7-6 (7-5), 4-6, 6-2, while 20th-seeded Belgian Kirsten Flipkens upended the eighth-seeded Kvitova in 4-6, 6-3, 6-4 fashion on the famed grass of Centre Court, where the retractable roof was closed because of rain on Day 8.
Playing with her right thigh heavily taped, Radwanska needed 2 hours, 43 minutes to stave off the 31-year-old Li, including a grueling 65-minute opening set. The Pole ultimately converted on an eighth match point to improve to 11-1 here over the last two years.
"If it's the end of a Grand Slam you don't really think about the pain or anything else," Radwanska said of the leg injury. "You just fight until the end. That's what I was doing today."
The 24-year-old Radwanska is now 5-6 lifetime against Li, including a 2-1 record at Wimbledon and 2-2 mark in Grand Slam action. The Polish star improved to 2-2 in her career Wimbledon and 2-7 in her career Grand Slam quarterfinals.
Li was this year's Australian Open runner-up to Victoria Azarenka, captured the French Open title in 2011, and was also an Aussie Open runner-up in '11.
She's now 0-3 in her career Wimbledon quarters.
Radwanska reached her first-ever Grand Slam final here a year ago, losing to Serena Williams in three sets. She made history by becoming the first-ever Pole to reach a Wimbledon final and the first Polish Grand Slam finalist in 73 years.
Radwanska's semifinal opponent on Thursday will be giant-killer Sabine Lisicki.
The 27-year-old Flipkens stunned the left-handed slugger Kvitova in 2 hours, 5 minutes to secure a berth in her first career Grand Slam semifinal. The crafty Belgian tallied three service breaks, compared to two for her Czech counterpart, mixing in an array of drop shots and slices on the way to victory.
The 23-year-old Kvitova was seeking a trip into a third Wimbledon semi in four years. She's now 2-2 in her career Wimbledon and 4-3 in her overall major quarterfinals.
Flipkens had never reached a Grand Slam quarterfinal prior this week. Her previous-best showing at Wimbledon was a third-round appearance in 2009.
"It's ridiculous! Last year I didn't even get into qualifying," said Flipkens, who was sidelined with blood clots in her legs. "To be a semifinalist at Wimbledon, it cannot be better.
"The people believing in me, I can count on one hand. It's amazing."
Up next for the surprising Belgian will be 15th-seeded Frenchwoman Marion Bartoli, who took out the last American still standing at the All England Club, 17th-seeded Sloane Stephens, 6-4, 7-5, following a lengthy rain delay on Court 1. The bizarre match featured eight successive breaks of serve at one point.
The 28-year-old Bartoli was the 2007 Wimbledon runner-up and was also a quarterfinalist here in 2011. She's now 3-3 in her career Grand Slam quarters.
The 20-year-old Stephens was an Aussie Open semifinalist in January and played in her first-ever Wimbledon quarterfinal on Tuesday.
For the second time in three majors this year, Stephens was the last American standing in either the men's or women's singles draws.
Meanwhile, less than 24 hours after stunning the world No. 1, defending champion and five-time overall Wimbledon titlist Williams, the 23rd-seeded Lisicki stayed hot at this fortnight and reached her second semifinal here in three years by tackling Estonian Kaia Kanepi 6-3, 6-3 in 64 minutes on Court 1. The 23-year-old German broke Kanepi four times, while the Estonian managed only one break in the setback.
"I was ready today," Lisicki said. "I knew from the past, out of experience, that I needed to make the switch quickly to be ready, and that's what I did."
Tuesday marked the first-ever meeting between Lisicki and Kanepi, who recently returned to action after being sidelined for several months because of a heel injury.
Kanepi is now 0-5 in her career Grand Slam quarterfinals, including 0-2 at Wimbledon.
The big-serving Lisicki has reached at least the quarterfinals in her last four trips to Wimbledon.
The Florida resident Lisicki will meet Radwanska for a third time, as the two women split their first two career meetings, both on hardcourts, while Bartoli and Flipkens will meet for the first time on Thursday.
For the first time in 15 years, all four women's semifinalists in a Grand Slam event are seeking a first-ever major singles title.
In women's doubles on Day 8, the top-seeded tandem of Sara Errani and Roberta Vinci lost to a 16th-seeded duo of German Julia Goerges and Czech Barbora Zahlavova Strycova, 3-6, 6-3, 6-2, in the third round. The Italians Errani and Vinci are the reigning Aussie and U.S. Open champs.