World number one Jelena Jankovic will face defending champion Elena Dementieva in the Kremlin Cup semi-finals after both players had to fight hard to overcome their unseeded opponents Friday.
Dementieva was the first player to reach the last four, eliminating fellow-Russian Nadia Petrova 6-4, 4-6, 7-6.
The third seed won the opening set and led 4-1 in both the second and third sets but allowed her compatriot to come back each time.
But the Olympic champion, who also beat Petrova in three sets in this year's Wimbledon quarter-finals, was not to be denied as she held her nerve to clinch the tiebreak 8-6 after nearly three hours.
"She changed tactics in the second set and started to play more aggressively," said Dementieva.
Jankovic, making her Moscow debut, also had to use all her big-match experience to beat Italian Flavia Pennetta 7-6, 6-3.
Pennetta led 3-1 in the second set before the Serb, who replaced Serena Williams at the top of the WTA rankings on Monday, reeled off five successive games.
Men's world number 98 Misha Zverev, who has earned just over 381,000 pounds in career prize money, guaranteed himself at least $51,300 from this week by reaching his first ATP semi-final with a thrilling 6-4, 3-6, 7-5 win over Serb Viktor Troicki.
The Moscow-born 21-year-old, who moved to Germany with his family at the age of four, saved two matchpoints, battling back from 1-5 down in the decider.
"I've lost matches after throwing away a 5-1 lead but I've never won from 1-5 down in the third set so this is a first for me," he told reporters.
The reward for his heroics will be a clash with either defending champion and top seed Nikolay Davydenko or former world number one Marat Safin, who were playing later Friday.
Men's fourth seed Paul-Henri Mathieu, who won here in 2002, was forced to retire from his all-French quarter-final against 35-year-old Fabrice Santoro because of illness while trailing 6-3, 2-0.
Women's seventh-seeded Russian Vera Zvonareva also went through after beating Slovak teen-ager Dominika Cibulkova, who upset world number five Ana Ivanovic in the previous round, 7-5, 6-4.
Zvonareva, who reached the last four at the $2.38-million indoor tournament for the first time, will take on the winner of another all-Russian encounter between second seed Dinara Safina and fifth seed Svetlana Kuznetsova.