Top seed Lleyton Hewitt [ Images ] 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 [ Images ], 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 [ Images ] 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 [ Images ] 7-6, 6-7, 6-2 in Friday's last quarter-final.