Sydney - Serena Williams felt the effects of a long night match and the searing heat as the top seed crashed out of the Medibank International 6-3, 6-1 to Olympic champion Elena Dementieva on Thursday.

Williams, second in the world, was coming off a nearly three-hour effort the previous evening against Danish teenager Caroline Wozniacki, where she had to save match points for the second time this week.

The 27-year-old American's early season fitness wilted in the summer heat as Dementieva went through into the final - a repeat of the Beijing Olympic gold medal match - against Dinara Safina despite firing six double-faults.

The all-Russian women's showdown will be the 10th between the compatriots, with Safina holding a thin 5-4 lead in the series. Dementieva won their last two meetings in Doha and Beijing in 2008.

The win over Williams was the third in succession against the American for Dementieva, fourth in the world to Safina's' third. The weary Williams lost her serve five times while breaking her opponent only once.

Safina had more work to do in her semi as she controlled Japanese veteran Ai Sugiyama 6-4, 7-6 (7-3), a third straight win in that series for the Russian who played the Hopman Cup final last weekend with her big brother Marat Safin.

Dementieva will be looking for her 13th career title after winning three in 2008 and starting this season with the Auckland honours last weekend. (dpa)