Ronnie O'Sullivan is in danger of crashing out of the World Snooker Championship after Mark Williams established a 6-2 lead in their quarter-final clash on Monday. Williams, bidding for a fourth world title, reeled off five consecutive frames at Sheffield's Crucible Theatre to take control of the best-of-25 tie. There was nothing to separate the veteran duo before the mid-session interval as they shared the opening four frames, which included a century from five-time world champion O'Sullivan. But just 24 hours after criticising the lack of quality opposition outside the sport's top stars, O'Sullivan endured a poor run that puts his World Championship challenge in jeopardy.

Williams edged a scrappy fifth frame before propelling himself into a healthy position with breaks of 72, 56 and a superb 130. Meanwhile, Kyren Wilson moved into a 10-6 lead over defending champion Judd Trump in their quarter-final. Trailing 5-3 from the opening session, a frustrated Trump continued to be kept at arm's length by Wilson as the pair initially traded frames. Wilson responded to Trump's knock of 73 with a break of 65 to maintain his two-frame advantage.