While day three of the OUE Singapore Open was marked by a series of upsets, it was business as usual on Friday, as both the men's and women's defending champions progressed to the semi-finals.

Reigning men's champion Simon Santoso reached the final four after defeating 2013 SEA Games gold medallist Tanongsak Saensomboonsuk of Thailand 21-10, 21-19 in their quarter-final clash.

His semi-final opponent is Japan's Kento Momota, whose quarter-final opponent H. S. Prannoy withdrew owing to injury.

Hong Kong's Hu Yun, who knocked out China's world No. 1 Chen Long on Thursday, will face India's Parupalli Kashyap in the other semi-final.

Hong Kong's world No. 13 beat China's world No. 12 and 2009 junior world champion Tian Houwei 17-21, 21-18, 21-10.

Kashyap advanced courtesy of a 21-6, 21-17 win over France's Brice Leverdez.

Women's title holder Wang Yihan also secured her semi-final berth, although she had to be in top form against Thailand's Ratchanok Intanon, who took the first set and stretched the Chinese world No. 7 all the way before succumbing 21-10, 19-21, 12-21.

In the rubber set, Wang held her nerve and clinched the match after racing to a 13-8 lead. Her semi-final opponent is Chinese Taipei's Tai Tzu-ying.

Wang's compatriot, world No. 4 Wang Shixian, also booked her spot in the semi-final after beating Japan's Akane Yamaguchi 21-18, 21-17. She will play team-mate Sun Yu in the other semi-final.

Singapore's mixed doubles pair Danny Bawa Chrisnanta and Vanessa Neo failed to reach their first Superseries semi-final as they lost 10-21, 14-21 to Indonesia's Tontowi Ahmad and Liliyana Natsir in the day's final match.

The OUE Singapore Open continues on Saturday at the Singapore Indoor Stadium.