Judd Trump lost 6-0 to world number 120 Michael Wild in the International Championship qualifiers in Barnsley.
Trump, ranked seven in the world, won the event in 2012 but has failed to reach the final stages in China later this month.
Wild, 34, took advantage of Trump's error-strewn display as breaks of 63, 82 and 62 helped seal victory.
"It's the best moment of my career by far. It's hard enough beating Judd, let alone 6-0," said Wild.
"I felt nervous before the game, but once I got into it and won the first frame I relaxed.
"Judd didn't really get my chances - I kept him out as much as I could."
Former world champions John Higgins and Ken Doherty joined Wild in qualifying for the third ranking event of the season, which starts in Daqing on 25 October.