Mark Selby pulls out of China Open as O'Sullivan beats Williams
Mark Selby has withdrawn from the China Open with a neck injury.
The world number one had been due to play Ding Junhui in the last 16 but is returning to England for treatment.
"I struggled through my first-round match and I don't want to do any more damage, especially with the World Championship coming up," he said.
Ronnie O'Sullivan crushed Mark Williams 5-1 in their second-round match, while world number six John Higgins was edged out 5-4 by Peter Ebdon.
World number two Williams has not beaten O'Sullivan for 10 years and missed an opportunity to level the tie at 2-2.
O'Sullivan, who now leads their head-to-head meetings 23-7, will meet the Welshman again in the second round of the World Championship if both players win their first-round matches.
Stephen Maguire will face O'Sullivan in the quarter-finals after coming through a tight encounter against Ricky Walden 5-4.
Meanwhile, Ebdon sent Higgins crashing out by taking a thrilling final frame.
Higgins got the snooker he required to stay in the match but world number 28 Ebdon held his nerve to claim victory.
He will play Neil Robertson in the quarter-finals after the Australian won the final two frames to beat Stephen Hendry 5-3.
Defending champion Judd Trump,who saw off Mark Selby in last year's final, won three frames on the trot to beat Stuart Bingham 5-3 and earn a last-eight clash with Stephen Lee.
Chinese 18-year-old Lu Ning was unable to add to his shock win over Shaun Murphy in the first round as he went down 5-1 to Ali Carter, who will play Ding for a place in the semi-finals.