Venus advances to semis at Pan Pacific Open
Williams, whose previous best in Tokyo was the quarterfinals in 2004, broke Bouchard with a forehand down the line to go up 5-2 in the third set and held on to win the match that lasted three hours at Ariake Colosseum.
"She played so well," Williams said. "She's going to be a great player -- she's already a great player -- and it was just a fight to the end."
Also, fourth-seeded Caroline Wozniacki beat Lucie Safarova of the Czech Republic 2-6, 6-3, 6-2 to set up a semifinal with fifth-seeded Angelique Kerber of Germany, who ousted second-seeded Agnieszka Radwanska of Poland 6-4, 6-4. Wozniacki and Kerber are 3-3 in head-to-head matches. Wozniacki won their semifinal match at Indian Wells in March.
The 19-year-old Bouchard put Williams on notice when she built a 3-1 lead in the quarterfinals. Williams fought back to break her three times in their first meeting.
In the second set, Bouchard capitalized on her second set point, winning the tiebreak 7-4.
"I was just fighting until the end," Williams said. "It was disappointing to lose the second set, but to win the third set is the goal, so I'm happy."
Copyright 2013 by The Associated Press
This story is from ESPN.com's automated news wire. Wire index