Bali, Indonesia -- (Sports Network) - Veteran Japanese Kimiko Date Krumm upset fifth-seeded Spaniard Anabel Medina Garrigues in Thursday's round-robin action, while France's Aravane Rezai secured a berth in Saturday's semifinals at the $600,000 Tournament of Champions tennis event.

The 12th-seeded 39-year-old Date Krumm straight-setted Medina Garrigues in 6-4, 6-3 fashion on the indoor hardcourts at the Bali International Convention Centre.

A milder upset came when a 10th-seeded Rezai topped eighth-seeded Hungarian Melinda Czink 6-3, 7-5 to improve to 2-0 for the week and move into the final four here.

In other Day-2 round-robin play, sixth-seeded Spaniard Maria Jose Martinez Sanchez overcame ninth-seeded Hungarian Agnes Szavay 4-6, 6-4, 6-0 and seventh-seeded Israeli Shahar Peer downed 11th-seeded Slovakian Magdalena Rybarikova 6-1, 7-6 (7-4).

Friday's round-robin action will pit top-seeded Frenchwoman Marion Bartoli against Peer, second-seeded Aussie Samantha Stosur versus Martinez Sanchez, third-seeded Belgian Yanina Wickmayer against Medina Garrigues and fourth- seeded German Sabine Lisicki versus Czink.

This five-day competition is a 12-woman round-robin affair, featuring four groups of three players. The field is comprised of the highest-ranked 10 players who have won at least one international tournament during the year and who did not participate in last week's exclusive 10-player Sony Ericsson Championships in Doha, as well as two wild cards.

The A Group features Bartoli (1-0), Peer (1-0) and Rybarikova (0-2), while B Group boasts Stosur (1-0), Martinez Sanchez (1-0) and Szavay (0-2), C Group features Wickmayer (1-0), Medina Garrigues (0-1) and Date Krumm (1-1), and D Group is made up of its' winner Rezai, Lisicki (0-1) and Czink (0-1). Rybarikova and Szavay have been eliminated from contention for the semis.

An undefeated winner this week would earn $200,000.