Petra Kvitova rallied to defeat Venus Williams 3-6, 6-3, 7-6 (7-2) and advance to the Pan Pacific Open final on Friday.
Fifth-seeded Angelique Kerber of Germany beat fourth-seeded Caroline Wozniacki 6-4, 7-6 (7-5) in the other semifinal.
Kerber leads the head to head series 2-1, with all of the matches being played last year.
The seventh-seeded Kvitova won when Williams’ return was long to close the match at Ariake Colosseum in 2 hours, 24 minutes.
Kvitova dominated the tiebreak, jumping out to 6-0 lead. Williams got two points back before Kvitova capitalized on her third match point.
“I am really happy with how I played today,” Kvitova said. “It was a very close match, and every game was up and down.”
Kvitova held off 11 break points.
Williams was bidding for her first title since last October, when she won in Luxembourg.
“I was probably a little tired,” said Williams, who endured a 3-hour, three-set match on Thursday. “But I don’t think it affected the match. She played two matches yesterday, so no doubt was a little tired, as well.”
Serena year-end No. 1
Serena Williams has secured the year-end world No. 1 ranking for the third time in her career, the WTA said Friday.
The 32-year-old American, who now has a career total of 55 titles, including 17 major wins, also achieved the feat in 2002 and 2009.
Williams joins Justine Henin and Martina Hingis as a three-time year-end number one, with only Steffi Graf (8), Martina Navratilova (7), Chris Evert (5) and Lindsay Davenport (4) ahead of her.
“Serena has proven time and time again throughout her career that she is an incredible champion, both on and off the court,” WTA chairman and CEO Stacey Allaster said in a statement.
“This season she continues to rewrite the record books, proving that she is one of the sport’s greatest athletes of all-time.”
Williams has topped the rankings six times and on Monday, she will have held the top position for a total of 156 weeks, the WTA said.
In February, she became the oldest world number one since computer rankings were introduced in 1975.
And this year Williams also became the first woman to surpass $9 million in prize money in a single season, pushing her career earnings past $50 million.
Williams’ total of 55 career singles titles means she is tied for seventh with Davenport and Virginia Wade on the all-time list.
Navratilova holds the record for the most singles titles with an astonishing 167, including 18 Grand Slams. The Open-era record belongs to Graf, with 22 major victories.