There will be no all-Williams final at Wimbledon this year.
Defending champion Serena has a good chance of playing for her fourth title on Saturday, but big sister and five-time winner Venus will be a spectator this time.
Venus was ousted in the quarterfinals Tuesday, losing 6-2, 6-3 to 82nd-ranked Tsvetana Pironkova of Bulgaria.
Venus, seeded second, had reached the Wimbledon final in eight of the past 10 years. This time, she was undone by a slew of unforced errors and double-faults in her worst loss at Wimbledon in terms of games won — five.
In another surprise, 21st-seeded Vera Zvonareva of Russia rallied past two-time U.S. Open winner Kim Clijsters 3-6, 6-4, 6-2 to reach her first Wimbledon semifinal, where she will face Pironkova.
Serena Williams avoided the wave of upsets, beating China's Li Na 7-5, 6-3 and moving closer to her 13th Grand Slam championship. The top-seeded Serena had 11 aces to take her tournament total to 73, breaking the record of 72 she set last year. She had 21 winners and just six unforced errors.
"I always serve well at Wimbledon, but this is the first time I've ever served this well so consistently,'' Serena said.
Her semifinal opponent is 62nd-ranked Petra Kvitova of the Czech Republic, who saved five match points before beating Estonian qualifier Kaia Kanepi 4-6, 7-6 (8), 8-6.
"I'm very happy,'' said the 20-year-old Kvitova, her voice shaking. "I can't believe it. It's something incredible.''
It's the first time two unseeded players have reached the women's semifinals at Wimbledon since 1999.
The Williams sisters have played each other in four Wimbledon finals, with Serena winning for the third time last year. With Venus out, Wimbledon is guaranteed at least one first-time Grand Slam finalist among the three other contenders.
With all the other big names gone, Serena Williams is the overwhelming favorite for the title.
"It's not mine to lose, it's mine to win if I can get it,'' she said. "There's three other people that are vying to win it. They have just as good a chance as I do.''
Serena said she's not surprised the left-handed Kvitova got this far.
"She's a really tough player, especially on grass,'' she said.
Kvitova doesn't give herself much of a chance.
"She won here I don't know how many times,'' she said. "I lost against her in the Australian Open. It was very quick. I'm not favorite, so I can play just my game and just play and enjoy.''
Venus never got going against the 22-year-old Pironkova, who is the lowest-ranked player remaining in the women's draw and had never previously passed the second round in 18 previous Grand Slam appearances.
"I just didn't get enough balls in today,'' said Williams. "I let it spiral and didn't get any balls in. I had a lot of opportunities, a lot of short balls and I seemed to hit each one out.
"If there was a shot to miss, I think I missed it. ... I didn't bring my best tennis today.''
Pironkova also beat Venus Williams in the first round of the Australian Open in 2006, but few gave her a chance of replicating the feat on the grass of Wimbledon, where Williams has dominated for a decade.
But Williams was clearly off her game, committing 29 unforced errors compared to just six for Pironkova. Williams had five double-faults, including back-to-back doubles in two games.
She also hadn't lost at a Grand Slam to a player outside the top 80 since that defeat in Australia to Pironkova, then ranked No. 143.
"Honestly, I think no one expected me to play semifinal in Wimbledon and to beat Venus Williams like that,'' said Pironkova, who denied Williams her 200th career Grand Slam match win. "Coming here I really just wanted to play a good game, to maybe win one or two rounds.
"I still cannot believe that I reached the semifinals. This is truly like a dream to me.''
Pironkova became the first woman representing Bulgaria to reach a Grand Slam semifinal in the Open era. Bulgarian-born Manuela Maleeva-Fragniere was representing Switzerland when she reached the U.S. Open semifinals in 1992 and 1993.
Pironkova broke Williams twice in the first set, winning four straight games after a 2-2 tie, finishing the set with a backhand passing shot down the line.
After Williams broke to go up 2-1 in the second set, it looked as though she might be able to take command. But Pironkova broke right back in the next game, which included the shot of the match. After Williams hit a forehand drop volley, the Bulgarian raced forward and flipped a backhand lob winner over Williams' head. Pironkova swung her arm in an uppercut celebration.
Down 5-2, Williams saved two match points, but Pironkova served out the match in the next game. After Williams missed a forehand volley, Pironkova squealed and fell on her back on the turf.
In Serena's match, the momentum swung the American's way after Li's game fell to pieces while serving at 5-5, 40-love in the first set. Li hit a forehand into the net, a forehand wide, had two straight double-faults and a forehand volley error to hand Williams the break. Serena served out the set in the next game.
Serena was broken while serving for the match at 5-2 in the second set, but broke right back in the next game to close it out.
Zvonareva rallied for her first win over Clijsters in six meetings.
Clijsters, returning to Wimbledon for the first time since 2006 after coming out of retirement, beat fellow Belgian Justine Henin on Monday and was viewed as a potential title threat.
The eighth-seeded Clijsters looked in command after sailing through the first set, but the match turned in the Russian's favor after she broke to go up 3-1 in the second.
Clijsters finished with 36 unforced errors, compared to 19 for Zvonareva.
"It's too bad I wasn't able to come up with my best at the important time in the match,'' Clijsters said. "She did. She was very consistent, didn't give me any easy mistakes. I gave her a few too many.''
