Lindsay Davenport will take over the world number one spot from Amelie Mauresmo when the rankings are released next week after brushing aside Dinara Safina 6-4, 6-2 on Thursday to reach the Kremlin Cup quarter-finals.
The 18-year-old Russian, the younger sister of 2000 U.S. Open champion Marat Safin, put up brave resistance in the first set, but the second seed still managed to run out a comfortable victory after 86 minutes.
The 28-year-old American, who trailed Mauresmo by 15 points at the start of the week, only needed to win her opening match in Moscow to take the top spot after the Frenchwoman withdrew from the $2.3 million tournament with a thigh injury.
"Of course I'm excited but I'd like to be able to keep going and win the tournament as a new number one and not be completely satisfied by just winning today's match," said Davenport, who first made it to world number one six years ago.
Fifth seed Elena Dementieva also eased through to the last eight with a 6-3, 6-3 win over Croatian qualifier Sandra Mamic to earn an eagerly-awaited rematch with fellow Russian Svetlana Kuznetsova, whom she lost to in the U.S. Open final.
Dementieva, who celebrates her 23rd birthday on Friday, said she wants to win badly.
CLOSE FRIEND
"I won't be celebrating if I don't beat her tomorrow," said the blonde Russian, who also lost in this year's French Open final to compatriot and close friend Anastasia Myskina.
Defending champion and third seed Myskina recovered from a slow start to oust her Russian Fed Cup team mate Elena Likhovtseva 2-6, 6-1, 6-0 and set up yet another all-Russian quarter-final with sixth seed Vera Zvonareva.
Former world number one Venus Williams also advanced, beating 18-year-old Vera Douchevina, one of several young Russians who have taken tennis by storm this year, 6-0, 6-4.
The reward for the seventh-seeded American is a quarter-final meeting with yet another Russian, Elena Bovina.
On the men's side, Greg Rusedski, trying to get his tennis career on track after battling through various injuries and doping allegations, crushed Filippo Volandri, one of the hottest players on the tour at the moment, 6-2, 6-4 in 62 minutes.
The Canadian-born Briton hit only three aces but won 84 percent of his first serves in his second round clash with the seventh seed Italian, who earned the ATP Player of the Month honours for September after moving 17 positions in the ATP Race.
Rusedski will now meet second seed Swede Joachim Johansson, the highest seed left in the men's draw, in Friday's quarter-finals after top seed and home favourite Marat Safin was bundled out by unseeded Czech Radek Stepanek on Wednesday.
Third seed Dominik Hrbaty and fifth-seeded Mikhail Youzhny also reached the last eight in contrasting fashion.
Russia's 2002 Davis Cup hero Youzhny had little trouble with unseeded Swede Jonas Bjorkman, winning 6-4, 6-2, while Slovak Hrbaty outlasted Belarussian Vladimir Voltchkov in a see-saw battle 4-6, 7-5, 7-6 in the last match of the day.