Ronnie O'Sullivan crashed out of the Royal London Watches Grand Prix after being crushed by Australian Neil Robertson.
O'Sullivan, last season's runner-up, was thumped 5-1 at the Aberdeen Exhibition and Conference Centre as Robertson secured a place in his first ranking event semi-final.
The world number three, who earlier in the week declared he wanted to be like gunslinger Billy the Kid, admitted: 'He was on fire. He blew me away.
'You have to give the geezer credit. He didn't miss a ball.
'Sometimes you can come up against someone like that and he deserved his win. I wish I could have given him a better game, but I didn't.
'You can't just turn up with your B game and think you're going win, you can't.
'Today he played fantastic. If he carries on playing like that he'll fancy his chances of winning the tournament. He was a hard man out there today.'
Robertson, who had lost all five of his previous ranking event quarter-finals, started the better and, with runs of 31 and 32, took the opener.
A break of 46 followed as the Melbourne cueman went 2-0 ahead before O'Sullivan hit back with a 69 break to reduce his arrears.
But Robertson won the fourth frame with a 42 break to lead 3-1 at the interval and further breaks of 71 and 65 followed as the world number 13 fired his way into the semis.
'I will definitely say this is the best performance of my career so far,' said an understandably delighted Robertson.
'I'm very happy with the way I played. I've scored heavier in matches and maybe played better, more explosive stuff, but I think playing like that against someone like Ronnie O'Sullivan is so much harder to do.'
Stoke qualifier Jamie Cope became the second player through to the last four following a nailbiting 5-4 quarter-final victory over Joe Perry.
The player nicknamed the 'Shotgun', due to his speed around the table, 21-year-old Cope fought back from 2-1 down to lead 4-2 and had chances for a 5-2 victory.
But 2001 European Open runner-up Perry won the next two frames and pocketed a 119 break in the eighth to level at 4-4.
However, Cope held his nerve with a yellow-to-pink clearance to seal a place in his first-ever ranking event semi-final and believes he can go on and clinch the title.
'I just had to hold myself together,' said a relieved Cope, who had earlier knocked in breaks of 50, 62 and 53 to edge closer to a place in the next round.
'If I can carry on playing alright, I can win it.'
Defending champion John Higgins was stunned 5-2 by Romford left-hander Mark King on a day of shocks.
Having seen runner-up O'Sullivan crash out earlier in the afternoon session, last year's Grand Prix and Masters champion was also sent packing at the quarter-final stage in his first defeat by King for 12 years.
'It went wrong all night. My concentration was all over the place from the first frame. That was the telling point in the match,' admitted Higgins.
Higgins started in the worst possible fashion with a new record of 12 consecutive misses in a televised match eclipsing his opponent's record of 11 misses against Stephen Lee at the 1997 UK Championship at the Preston Guild Hall.
And after King added a break of 66 the first frame was gone, before he added the next with runs of 38 and 26.
A 69 break followed to make it three frames on the bounce, and then Higgins strangely conceded the fourth frame only 44 behind and with 51 points available.
It got slightly better after the interval as Higgins reduced his arrears with back-to-back breaks of 55 to trail 4-2.
But it only delayed the inevitable as world number 29 King secured a place in his seventh ranking event semi-final with a 71 break in the seventh and deciding frame. One more victory and he would have reached only his third ranking event final.
