Chinese wildcard Zheng Jie provided an absorbing sub-plot to Williams sister domination on quarter-final day at Wimbledon on Tuesday.
Zheng beat Czech Nicole Vaidisova 6-2, 5-7, 6-1 to become the first Chinese player to reach a Grand Slam singles semi-final and the first woman to go so far at Wimbledon after requiring a special invitation from the All England Club.
During an unpredictable tournament riddled with shocks the one constant has been the ruthless efficiency of Venus and Serena Williams and now they look odds on to contest their third Wimbledon final here on Saturday.
Venus, champion here four times and twice runner-up to her younger sister, was engaged longer than expected in beating Thai surprise Tamarine Tanasugarn 6-4, 6-3 before Serena made mincemeat of Poland's Agnieszka Radwanska 6-4, 6-0.
Serena will play Zheng in the semi-finals while Venus must get past fifth seed Elena Dementieva after she survived a mid-match wobble to beat fellow Russian Nadia Petrova 6-1, 6-7, 6-3 and reach Wimbledon's last four for the first time.
"I was like, Oops, I did it again; I'm out of the semi-finals," Dementieva, who lost to Dinara Safina in the quarter-finals at Roland Garros this year after having a match point, told reporters.
"I was so tight. I suddenly started to think about the French Open quarter-finals and it was difficult [to get that out of my head]. It was so exhausting."
Dementieva threw away a 5-1 lead in the second set but instead of capitulating as she did against Safina she managed to steady her nerves and regain control.
Despite being the highest seed to skip past the banana skins that have tripped many of the top players, Dementieva will start as underdog against seventh seed and defending champion Venus.
The American, who like her sister has not dropped a set at this year's championships, was not at her best against Tamarine but had plenty in reserve when it was required.
Tamarine, at 31 the oldest player to reach the last 16 and the first Thai in a Grand Slam quarter-final, played admirably despite being outgunned by Venus and had she taken one or two more of the numerous break points her patient baseline game provided, another shock might have been possible.
"I expect when times are tough to get going, those break points you just have to play better and I'm really blessed to have a serve that gets me out of those issues," Venus told reporters, playing down a late scare when she appeared to pull up sharply after a slide.
"I'm fine. I mean, I'm walking around on two legs, doing good, so I'm not really concerned right now."
Zheng repaid the organisers gift of a wildcard into the tournament by knocking out world number one Ana Ivanovic in round three and claimed her fourth seed of the championships with a calm and controlled defeat of Vaidisova.
She appeared to be tiring in the second set as Vaidisova became more aggressive but was the more resilient player in the decider and raced to victory.
Former Wimbledon doubles champion Zheng, who missed the 2007 season with an ankle injury, turns 25 on women's finals day but with Serena Williams in a mean mood she is unlikely to be celebrating it on Centre Court.
"Serena is an outstanding player, and I haven't found any weak link about her. But as a first time semi-finalist, I would rather enjoy this than anything else," Zheng said.
Sixth seed Serena was too powerful, too consistent and too fired-up as she continued to torment the Radwanska family.
In the second round she beat Urszula Radwanska, Agnieszka's younger sister, while in the doubles she and Venus beat Agnieszka and her partner Marta Domachowska.
They may still have some work to do if Saturday is to become a family affair on Centre Court but Serena said she already had a trick up her sleeve for her sister.
"I'm going to sabotage her and eat all the breakfast," she said. "I'll eat all the Wheaties so she doesn't have any chance, if we get that far."