Former world number one Venus Williams turned back the clock with some brutal hitting to overcome Canada's Eugenie Bouchard 6-3, 6-7, 6-3 Thursday and reach the semi-finals of the Pan Pacific Open.
The 33-year-old American, who won the last of her seven grand slam singles titles in 2008, recovered from a poor second set tiebreak with a series of electrifying shots and acrobatic volleys in the decider, completing victory with another ferocious forehand cross-court after a shade over three hours.
"It's hard to believe it's my first semi-final in Tokyo after all these years," said Williams, currently languishing at 63rd in the world after being diagnosed with an autoimmune disorder in 2011.
"Hopefully I can win it in a little less time. That's the goal."
Watched from the royal box by five-times Pan Pacific champion Martina Hingis, Williams showed flashes of the form that swept her to five Wimbledon titles between 2000 and 2008 as she continued her purple patch in Tokyo.
She won her last singles title -- her 44th -- at last October's Luxembourg Open.
"I've played against so many great players over a couple of generations, it seems," added Williams, who giggled when reminded Thursday was sister Serena's 32nd birthday.
"We always forget each other's birthdays. Serena's getting old, like me," smiled Venus. "She's an inspiration to me.
"I've put a lot into the game and I'm not going to give it up easily. As a professional athlete you have a window. My window's still open and I'm going to take advantage of it."
Williams upset top seed Victoria Azarenka in the second round of the $2.3 million event. But the 19-year-old Bouchard, ranked 46th in the world, pushed her hard, taking the second-set tiebreak 7-4.
"Actually I'm surprised I'm able to play these matches, I can't lie," confessed Williams after her plans for karaoke and a visit to a nail salon were scuppered by her marathon quarter-final.
"It was just determination, adrenalin and desire. These three-hour matches really cut down on my social life."
Williams will face the 2011 Wimbledon champion Petra Kvitova in the last four after the seventh-seeded Czech thrashed Russia's Svetlana Kuznetsova 6-4, 6-1.
It was a quick return to court for both players after they were forced to play rain-delayed third-round matches in the morning.
"I don't remember ever playing twice in a day on the WTA tour," Kvitova told AFP. "But Venus played a three-hour match so tomorrow should be 50-50 physically. I'm looking forward to it."
Earlier, fourth seed Caroline Wozniacki, the 2010 Tokyo winner, advanced to the semi-finals with a 2-6, 6-3, 6-2 victory over Czech Lucie Safarova.
The Dane will meet Germany's Angelique Kerber in Friday's semi-finals following the fifth seed's 6-4, 6-4 defeat of second-seeded Pole Agnieszka Radwanska.