John Higgins, installed as favourite for the Travis Perkins UK Championship after Ronnie O'Sullivan's exit, was knocked out by a rejuvenated Ken Doherty in York.
The Scot, winner of the season's only previous ranking tournament, had been in superb form but came up against an opponent who played his best snooker for two and a half years in the 9-6 third-round victory.
Doherty began the match with a 107 break which set the tone for his performance, added two further centuries and took three consecutive frames from 6-6 with some flawless potting that never gave Higgins a chance to fight back.
"That's the best I've played since losing the World Championship final in 2003," said the Irishman, who has struggled since that 18-16 defeat to Mark Williams.
"I've had a very frustrating time because I don't feel any different from then apart from my confidence levels. For some reason that final knocked the stuffing out of me and it has taken a long time to get back.
"It's nice to get a resounding win on television against a player at the top of his form. I was fed up of having to talk to the press about defeats I've had but now I'm as chirpy as a parrot!
Higgins admitted there was little he could have done to stop the man who, in 1997, preceded him as world champion and was his victim in the final at Sheffield's Crucible Theatre the following year.
"Ken played fantastic snooker," said the world number six. "I can't recall him missing a ball when he had a chance of making a break and when someone does that it makes it very difficult for you.
"I didn't do a hell of a lot wrong and ultimately you have to realise it's just a game, especially when you see guys battling with cancer."
