World number three Ding Junhui's hopes of winning a fourth consecutive ranking title came to an end with a 6-4 loss to Ricky Walden at the UK Championship.
China's Ding had threatened to take the match into a decider, only to miss a vital pink, allowing Englishman Walden to clinch victory.
Walden will meet Mark Allen in the quarter-finals after he beat 2011 champion Judd Trump 6-4.
Four-time UK champion Ronnie O'Sullivan thrashed Robert Milkins 6-0.
O'Sullivan, the reigning world champion, will play Stuart Bingham in the last eight after the Englishman beat David Morris 6-1.
Elsewhere, defending champion Mark Selby beat Graeme Dott 6-2 to earn a meeting with Barry Hawkins.
World number one Neil Robertson will play Stephen Maguire in the last eight after the Australian beat Joe Perry 6-1.
Ding had arrived in York having won the Shanghai Masters, Indian Open and the International Championship in China and was trying to become the first player since Stephen Hendry in 1990 to win four ranking titles in a row.
Walden looked to have blown a chance when he missed a yellow in the 10th frame but was let off the hook when Ding missed a regulation pink, and left it over the middle pocket, allowing the Englishman to return to the table and seal the win.
"I couldn't believe it," Walden told BBC Sport. "I thought we were definitely in for a decider and luckily for me I got my chance.
"It was a tough game. He's flying at the moment, scoring so heavy and he's the man to beat, so when you do get your chance and you feel like you've blown it, there's nothing worse.
"I didn't play my best but I stuck in there."
Asked about the decisive pink, Ding said: "My cue action didn't work; the cue turned in my hand."
He added: "The match was not good today. It's difficult to play Ricky, he gave very few chances. Every frame he scored heavily and he didn't leave any long ones. It was good safety."
World number four Trump was frustrated to lose after a performance from Allen which he described as "awful".
Trump said: "It just turned into a bit of a club game. It's frustrating because I felt like so far, I've played the best snooker in the whole tournament."
Allen added: "I don't know how I've won that game. I was really poor from start to finish, but one of my qualities is that I don't give up.
"I'm pretty proud of myself for coming back from 4-2, even though Judd let me off the hook."