The semifinal lineup for the Saudi Arabia Snooker Masters, hosted at the Green Halls in Riyadh, has been confirmed. Four matches were played Thursday, featuring eight players: four from England, two from China, and one each from Australia and Wales. Chinese player Si Jiahui, ranked 22nd in the world, caused a major upset by defeating the legendary player Ronnie O'Sullivan, a top contender for the title, by the score of 6-4. The 22-year-old Si Jiahui will now face three-time world champion Mark Williams from Wales, who defeated England's Jimmy Robertson 6-0. In other matches, world number 1 Judd Trump continued his impressive form throughout the tournament, beating 2010 world champion Neil Robertson of Australia 6-3 and advancing to the semi-finals, where he will face his compatriot Shaun Murphy, the 2005 world champion. The semi-finals will begin Friday. Judd Trump and Shaun Murphy will compete at 2:00 PM, followed by a match between Si Jiahui and Mark Williams at 8:00 PM. Source: Saudi Press Agency