Ronnie O'Sullivan rued some "silly" misses after crashing out to Anthony Hamilton in the Bank of Communication Shanghai Masters today.
Nottingham player Hamilton had already beaten Stephen Maguire in the first round and added a more notable scalp by beating the three-time world champion 5-3.
He responded to O'Sullivan's opening 92 with breaks of 49 and 107 to go 2-1 ahead, before the three-time world champion made a 65 to level at the mid-session interval.
O'Sullivan also won the first frame back with a 73 but breaks of 94, 72 and 63 in the next three frames saw Hamilton over the line.
O'Sullivan said: "I had chances but missed some silly balls. It was a 50/50 game but he played well towards the end when it mattered.
"I'll go home and start again. I'm enjoying playing. It would be nice to be back at the top but I don't expect it. I'll just enjoy whatever is left of my career. I've got nothing left to prove and I'm not young any more."
Hamilton goes on to play Mark King, a 5-3 winner over Fergal O'Brien, in the quarter-finals.
Hamilton said: "There was a lot of pressure, the crowd love Ronnie so much here that it's like an exhibition, so it's hard to focus.
"He struggled and I played great, and that had to happen for me to win."
Mark Selby led a host of big names through to the quarter-finals with a 5-0 hammering of Jamie Cope. Breaks of 64, 110 and 70 helped Selby progress to the last eight.
World number one Mark Williams also progressed serenely with a 5-1 rout of Robert Milkins, highlighted by a break of 130.
Selby could take the top ranking this week, but Williams said: "My ambition last season was to get back to number one, but I'm not that worried about staying there now. My ambition now is to win more tournaments before I start slipping down the rankings again, and I especially want to win another world title."
Williams faces an all-Welsh quarter-final against Matthew Stevens, who hammered Martin Gould 5-1.
World champion John Higgins saw off Stuart Bingham 5-2 after a messy start to their match, clinching victory with his highest break of the match, 69 in frame seven.
"It was not the best standard, it was scrappy," said Higgins. "Stuart has been in good form so I was lucky that he wasn't at his best today."
Australian Neil Robertson awaits Higgins in the next round after the 2010 Crucible champion beat Michael Holt 5-2.
Shaun Murphy recorded his second successive 5-4 win, seeing off Northern Ireland's Mark Allen.
Murphy, who had to dig deep to overturn a 4-1 deficit against Dominic Dale in the first round, recorded the tournament's top break so far with a 143 and added a 102.