LONDON, Nov. 29 (Xinhua) -- World number one Mark Selby suffered a shock 6-3 defeat to amateur James Cahill in the first round of the UK Championship in York on Thursday.
The two-time former champion never played his best snooker, going behind 4-0 and 5-1 from the start before crashing out.
"It's a great win," said 22-year-old Cahill, ranked 126th in the world, after scoring his biggest win. "Hopefully I can take confidence from that."
"I was rubbish all match," Selby said. "I am devastated because it's a big tournament. I felt flat, which is strange."
China's Liang Wenbo, who made the final in 2015, wasted a 5-1 lead as Sam Baird put on a tremendous comeback to win 6-5.
Flu-stricken Ronnie O'Sullivan, who is bidding for a record seventh title, defeated Luke Simmonds 6-1. Two-time UK winner and reigning world champion Mark Williams had little trouble in beating his amateur opponent Adam Duffy 6-2.
2004 UK champion Stephen Maguire recovered from 3-1 down to beat Germany's Simon Lichtenberg 6-3. Barry Hawkins routed Jamie Clarke 6-0, while 2003 UK champion Matthew Stevens saw off Ross Muir 6-4.
Luca Brecel came from 3-0 down to beat Fan Zhengyi of China 6-4, while Iran's Hossein Vafaei edged out Ashley Hugill 6-5.
China's Yan Bingtao made a break of 106 in a 6-1 victory over Lukas Kleckers, while 2006 UK Champion Peter Ebdon struck 103 in a 6-2 win over Chris Totten.