Madrid, Spain:Russians Maria Sharapova and Anna Chakvetadze needed three-set victories to reach the semifinals at the Sony Ericsson Championships on Thursday.
Sharapova's 5-7, 6-2, 6-2 win over countrywoman Svetlana Kuznetsova also advanced unbeaten Ana Ivanovic.
Sharapova and Ivanovic will meet on Friday. The winner of the Red Group match will play Chakvetadze in the semifinals on Saturday.
The loser will face defending champion Justine Henin, who topped Yellow Group undefeated by crushing Wimbledon finalist Marion Bartoli 6-0, 6-0 - the first victory to love in the WTA season-ending championship's 35-year history.
Bartoli had replaced Australian Open champion Serena Williams, who withdrew with a left knee injury she aggravated in her brief opening match on Wednesday.
Chakvetadze, a first-time qualifier in the elite eight-women event, hung on to beat third-ranked Jelena Jankovic 6-4, 0-6, 6-3.
Sharapova, ranked sixth, pulled away from second-ranked Kuznetsova with breaks in the fifth game of both the second and third sets.
Sharapova improved to 4-3 against Kuznetsova, with three of those wins at the WTA's season-ending championship.
"I thought I did a good job in the first set, I had a little less match experience than her at the end but I stayed together, stayed tough and came through," Sharapova said.
She reached the semifinals for the fourth straight time since winning the championship on debut in 2004.
"I'm really happy I didn't just stay home and quit and not come out here," said Sharapova who came to Madrid with an oft-injured right shoulder. "I'm good, this is really good for me. This will only make me physically stronger."
Kuznetsova managed only 15 winners to Sharapova's 40, but broke in the 12th game to take the first set.
"I had my chances in the second set and I didn't use them," Kuznetsova said.
Top-ranked Henin hit 30 winners to Bartoli's two, and was happy to defeat the Frenchwoman in their first match since the Wimbledon semifinals.
"It was a great one, almost everything was perfect tonight," Henin said. "I had a lot of determination, I wanted to take my revenge."
Chakvetadze took advantage of Janokovic's errors to break her in the 10th for the first set.
After a talk with her coach, Jankovic came out aggressively in the second with a break of serve and didn't let up, dominating from the baseline and the net to take the next seven games.
But a double fault ended the run as the Russian, a winner of four titles this season, broke back to tie it at 1-1 in the third.
Chakvetadze sent a backhand out of reach down the line to break her fellow first-time qualifier to love for a 3-1 advantage. She clinched it when Jankovic sailed her 26th unforced error over the baseline.
"I don't think we played 100 percent, a very up and down match," Chakvetadze said.
Jankovic said her lack of preparation before the championships and an ongoing illness left her unprepared for the rigors of the tournament.
"I'm going on vacation next, which is the only positive. I look forward to doing anything else but tennis," said Jankovic, who won a career-high four titles in 2007.
On Friday, Jankovic plays Bartoli and Kuznetsova faces Daniela Hantuchova to wrap up group play.