LONDON, Feb. 15 (Xinhua) -- Four-time champion Ronnie O'Sullivan wasted a 3-0 lead as he was stunned 4-3 by Mark Davis in the second round of the Welsh Open snooker tournament in Cardiff on Wednesday.
Neil Robertson, who lost to O'Sullivan in last year's final, Shaun Murphy and Marco Fu also crashed out in the last 64.
"At 3-0 down it wasn't looking good," said Davis. "I just dig in, I never give up, you never know what can happen. You just battle on, even against Ronnie. I know I can win it if I play my game - there is no point talking about it, you have to go and do it. I have known that for a long time, I know how good I am, there is no reason I can't win it."
Robertson was edged out 4-3 by Welsh veteran Lee Walker despite making a tournament-high 143 and leading 3-1.
Murphy was defeated 4-2 by tour rookie Josh Boileau while Fu went down 4-0 against Ross Muir.
Chinese number two Liang Wenbo, the English Open champion, was beaten by Welshman Michael White 4-3 in a dramatic finish.
Former world champion Stuart Bingham beat Rory McLeod 4-2 while Barry Hawkins made a 113 in a 4-0 win over China's Tian Pengfei.