BEIJING - World No 1 Mark Selby withdrew from the snooker China Open due to neck injury on Thursday as Ronnie O'Sullivan stormed into the last eight after demolishing Mark Williams 5-1.

Mark Selby of England competes during the first round of the China Open snooker tournament in Beijing, March 27, 2012. [Photo/Xinhua]

Selby had been due to play local star Ding Junhui in the last 16 but has decided to pull out hours before the match, giving his opponent a bye into the quarter-finals.

"I have been suffering with neck pain and I struggled through my first round match," said the 28-year-old Englishman in a statement.

"I don't want to do any more damage, especially with the World Championship coming up, so I'm going back to the UK to get some treatment."

Selby, the beaten finalist in the China Open last year, also apologized to the local fans who have long anticipated the mouth-watering showdown.

"I'm absolutely gutted to have to pull out and to let down the Chinese fans as I was really looking forward to playing Ding tonight," he said.

The organizers promised that the fans who had bought Thursday's tickets could choose either to be refunded at full price or to watch Ding's quarter-final match on Friday.

Ronnie O'Sullivan of England competes against Mark Williams during the second round of the the China Open snooker tournament in Beijing, March 29, 2012. [Photo/Xinhua]

Earlier in the afternoon, world number two Williams, who has not beaten O'Sullivan for 10 years, missed an opportunity to level the tie at 2-2 and went on to lose 5-1 in front of a captivated table one crowd.

O'Sullivan, dubbed 'The Rocket', found his form and scored top runs of 77 and 66 as he set up a match with Stephen Maguire on Friday.

"Today was a bit better than yesterday," said O'Sullivan, "Form is a funny thing, as long as you're playing steady and consistently you give yourself a chance of winning."

Young starlet Judd Trump got past Stuart Bingham 5-3 while China's dark horse Lu Ning let down the fans, losing 5-1 to Allister Carter.

Trump, defending China Open champion, scored breaks of 59, 61, 90 and 53 and fought back from 3-2 down to book a meeting with current form player Stephen Lee, who outperformed Graeme Dott 5-3.

Lu Ning, 18, stunned Shawn Murphy 5-2 in the first round on Wednesday but the wild card failed to maintain the momentum against Carter in a bumpy heat.

"I played well yesterday, which gave me confidence and pressure as well," said Lu, "I thought I might have chance to win before this match and that made me a bit nervous."

Neil Robertson, seeking his first ranking title in China, also secured a place in the last eight after a 5-3 win over Stephen Hendry. He will next play Peter Ebdon, who sweated to beat world champion John Higgin 5-4.

Ding, who turns 25 on March 31, said that he felt very "sorry" for Selby's injury and exit.

"I've got well along with Selby, so I feel very sorry for him and wish him a quick recovery," he said.

As for being given a bye into the last eight, Ding thought it may not be all positive things. "Certainly it's good to have more rest, but on the other hand, if you rest too long, you'll possibly lose the form," he said.

The scheduled matchup should have been the third meeting between the home star and Selby in Beijing. Ding conquered Selby 5-3 in the second round in the 2010 China Open, but Selby avenged the following year with a 6-3 win in the semifinals.