Maria Sharapova thrashed her Russian compatriot Svetlana Kuznetsova 6-1 6-4 at the WTA Championships in Madrid to claim a 19th straight win.
US Open champion Sharapova has not lost since August
The world number two will now play Justine Henin-Hardenne in the first of Saturday's semi-finals.
The third-ranked Henin-Hardenne lost to world number one Amelie Mauresmo earlier on Friday.
Mauresmo fought back from a set down to win 4-6 7-6 (7-3) 6-2 and will meet Kim Clijsters in the second semi-final.
Clijsters, the 2002 and 2003 champion, routed Elena Dementieva 6-4 6-0 in the final match of the group stages.
Yellow Group standings
1. Mauresmo W2 L1 F4 A4
2. Henin W2 L1 F 5 A3
3. Hingis W1 L2 F4 A5
4. Petrova W1 L2 F3 A4
Mauresmo, the defending champion, finished above Henin-Hardenne in the yellow group.
"I'm very happy I hung in there to get to the semis, even with the bad start I had," said Mauresmo, the Australian and Wimbledon champion.
Martina Hingis finished third in the group and Nadia Petrova last after both recorded a win and two losses.
Mauresmo's win will come as some consolation for the disappointment of losing the number one spot which will be taken by either Henin-Hardenne or Sharapova when the year-end rankings are released next week.
Red Group standings
1. Sharapova W3 L0 F6 A0
2. Clijsters W2 L1 F4 A2
3. Kuznetsova W1 L2 F2 A4
4. Dementieva W0 L3 F0 A6
French Open champion Henin-Hardenne, who returned to action this week after two months out because of a calf injury, will clinch the top ranking if she reaches Sunday's final.
Sharapova, the US Open champion, is in the form of her life and had far too much for Kuznetsova in their red group encounter.
"It was really good to start so well," said Sharapova. "You can't fool around at the beginning of matches and you have to be strong from the beginning of the match."
The 19-year-old Sharapova must win the title and Henin-Hardenne, who reached the final of every Grand Slam event this season, lose in the semis for her to secure her first year-end top ranking.
606 DEBATE: Who will win in Madrid?