Top seed Lleyton Hewitt survived a tough start before overcoming Denmark's Kenneth Carlsen 6-7, 6-4, 6-3 for a place in the semi-finals of the Mercedes-Benz Cup on Friday.
The Australian on occasions lost his temper and argued with the chair umpire before completing the win. He will meet German Nicolas Kiefer, who came from behind to beat American eighth seed Vince Spadea 1-6, 7-5, 6-3, in Saturday's semis.
Hewitt's compatriot and Wimbledon finalist Mark Philippoussis, seeded fifth, downed fourth-seeded Brazilian Gustavo Kuerten 6-3, 3-6, 7-6 in their quarter-final thriller.
Philippoussis booked a meeting with seventh seed Wayne Ferreira, after the South African upset second seed Sebastien Grosjean of France 7-6, 6-7, 6-2 in Friday's last quarter-final.
