Defending champion O'Sullivan stopped at Welsh Open second round
Updated: 2017-02-16 11:01:32
Ronnie O'Sullivan reacts during the second round of the Welsh Open snooker tournament in Cardiff, Britain on Feb 15, 2017. [Photo/Agencies]
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.