Russian Nikolay Davydenko reached the quarterfinals of the Qatar Open

Defending champion Ivan Ljubicic of Croatia and top seed Nikolay Davydenko of Russia have reached the quarterfinals of the Qatar Open men's tennis tournament in Doha.

Ljubicic had an easy time when his opponent, Serbia's Janko Tipsarevic, withdrew with a fever. In the final eight, Ljubicic plays German Philipp Kohlschreiber, a 6-4, 6-1 winner over Italian Filippo Volandri.

Davydenko reached the round of eight with a 6-3, 6-3 win over Fabrice Santoro of France. The Russian plays compatriot Dmitry Tursunov, who advanced when his opponent Nicolas Kiefer of Germany withdrew with a shoulder injury.

In other matches, third seed Andy Murray of Britain scored a three-set win over Rainer Schuettler of Germany, 1-6, 6-0, 6-1. Murray plays Sweden's Thomas Johansson next. Johansson defeated Michael Berrer of Germany in straight sets 6-3, 7-5.

Stanislas Wawrinka of Switzerland reached the round of eight with a 6-2, 7-5 win over Christophe Rochus of Belgium. The Swiss player next faces Agustin Calleri of Argentina, a 6-3, 6-1 winner over Lee Hyung-taik of South Korea.

Some information for this report was provided by AFP, AP and Reuters.