Mark Allen's hopes of earning a place in the World Championship main draw is out of his control after a 6-5 defeat by Mark Williams at the China Open.
Williams won a final-frame decider by a single point, finishing with a clearance of 67 after Allen missed a regulation red when leading 66-4.
The Northern Irishman now requires results elsewhere to go his way if he is to remain 16th in the rankings.
Williams will now face Mark Selby in the quarter-finals.
World number one Selby defeated China's Lyu Haotian 6-1. Jack Lisowski, Kyren Wilson, Neil Robertson, Stuart Bingham, Barry Hawkins and Tom Ford also progressed to the quarter-finals in Beijing.
Williams made a blistering start to the last-16 contest with a break of 130 to capture the opening frame and the Welshman quickly opened up a 3-0 lead.
Allen recovered to force the match into a deciding frame and appeared to be in control after a break of 51 before missing a red that would have left Williams requiring snookers to win.
The defeat leaves Allen in the final automatic qualifying spot for the World Championships but he could yet by overtaken by the likes of quarter-finalists Ford and Lisowski.