Coral UK Open champion Phil Taylor was sensationally knocked out of the tournament by TV debutant Aden Kirk at the Butlins Minehead Resort on Friday.
But St Hens darters Stephen Bunting and Dave Chisnall are through to the fourth round, but Michael Smith lost to Peter Wright.
Taylor's below-par start to 2014, which has seen him lose four of his opening five Premier League Darts games so far this season, continued as he suffered a 9-7 Third Round loss to Kirk in the biggest upset in the 11-year history of the event.
The 22-year-old factory worker from Nottingham, playing in his first televised event since progressing through the PDC Unicorn Youth Tour, had to defeat Conan Whitehead and Gerwyn Price earlier on Friday just to set up the clash with Taylor.
However, he showed no nerves with a resilient display, opening the game with a 14-dart leg and leading 4-2 and 5-3 before Taylor hit back to level with an 11-darter - although he also incredibly burst his score on 130 twice in one leg by hitting double 12 on both occasions during that run.
Kirk regained the lead by finishing 88 on the bull, and though Taylor took out 109 and 96 to stay in the hunt, the youngster took out 60 on tops to secure an amazing scalp.
"I still can't believe it and it's a dream come true for me," admitted Kirk. "I'd had a couple of tough games already and I played well just to get through to play Phil, which was my aim coming here.
"But to beat him is amazing. Phil didn't play like he can do, but I took my chances and hit my doubles. My mum's a massive Phil Taylor fan and even she didn't think I'd beat Phil, but anything could happen now."
Kirk will now play in-form Premier League Darts leader Peter Wright, after the World Championship runner-up was a narrow 9-8 winner against another youngster, Michael Smith, earlier on Friday night - with the St Helens ace missing seven darts to claim victory in the deciding leg.
World Champion Michael van Gerwen had fewer problems as he overcame former World Youth Champion James Hubbard 9-1, and he now plays Andy Hamilton in an eye-catching fourth round game - after last year's UK Open runner-up came from 4-0 down to defeat Jelle Klaasen 9-8.
Two-time UK Open champions James Wade and Raymond van Barneveld impressed in their big Third Round wins, with the left-hander defeating Michael Mansell 9-1 with a 101 average and the Dutch ace following up his two earlier victories with a 9-3 defeat of Mick Todd.
Wade has been drawn with Belgian star Kim Huybrechts, who was a 9-5 winner against Ross Smith, while van Barneveld now takes on Bolton's Joe Murnan, who came from 7-4 down to win 9-8 against another Dutchman, Dirk van Duijvvenbode.
Lakeside Champion Stephen Bunting defied seven 180s from Kevin Dowling as he claimed a dramatic 9-8 victory in their Third Round game, with the Coventry thrower paying for missed match darts in the penultimate leg as the PDC newcomer took out 151 and then won the decider.
Bunting now plays Dean Winstanley in the Fourth Round, with the Yorkshireman claiming a 9-2 win over Andy Boulton in their last 64 clash.
While Boulton was knocked out, two fellow Rileys Amateur qualifiers did win through to the last 32, with Plymouth newcomer Simon Stevenson overcoming Belgium's Rocco Maes 9-6 to set up a clash with Welsh youngster Jamie Lewis, who was a 9-8 winner over Ireland's William O'Connor.
Hampshire's Paul Hogan won 9-3 against Dutch youngster Benito van de Pas and now plays former Lakeside Champion Mark Webster, who was a 9-5 winner against 2005 UK Open finalist Mark Walsh.
Another former Lakeside Champion, Holland's Christian Kist, enjoyed a winning UK Open debut as he saw off Spain's Antonio Alcinas 9-2, missing double 12 for a nine-dart finish during an impressive display.
Kist has been drawn in an all-Dutch Fourth Round tie against Vincent van der Voort, who was a 9-6 winner against Darren Webster in their Minehead contest.
Dave Chisnall and Mervyn King will clash in a tasty Fourth Round game following their wins over Justin Pipe and Karl Merchant, while Kevin Painter's 9-5 win over Richie Burnett sees him progress to play Andrew Gilding, who received a bye after his scheduled opponent Wes Newton was forced to withdraw through tonsillitis.
Two-time World Champion Adrian Lewis enjoyed a 9-5 win over Ronnie Baxter and now plays Belgian ace Ronny Huybrechts, who knocked out world number three Simon Whitlock 9-6.
Shropshire youngster David Pallett, who hit a nine-darter in qualifying for the UK Open, defeated Kevin McDine 9-8 in a see-saw contest and now plays Gary Anderson, the 2010 UK Open finalist who was a 9-3 winner against Andy Smith.
2012 UK Open champion Robert Thornton was a 9-3 winner in his all-Scottish clash with Jason Hogg, and he now plays Austrian number one Mensur Suljovic, who won by the same scoreline against Rileys Amateur Qualifier Tony Randell.
Northern Irish star Brendan Dolan was a 9-6 winner against Steve Beaton and now plays Nigel Heydon, whose return to form this year continued as he defeated Steve Maish 9-1.
Terry Jenkins, who followed up his nine-darter at the World Championship with another perfect leg during the UK Open Qualifiers, was a 9-4 winner over Stuart Kellett.
He now plays Paul Nicholson in the last 32, after the former Players Championship Finals winner came from 5-3 down to win 9-5 against emerging County Durham ace Adam Hunt.
World Championship quarter-finalist Ian White's narrow 9-8 win over Peter Hudson moved him into the last 32, where he now plays Alex Roy after the UK Open veteran enjoyed a 9-1 win over Nick Fullwell.
Saturday afternoon's Fourth Round will be followed in the evening session at the Butlins Minehead Resort by the Fifth Round, as players bid to win through to Sunday's final stages of the ITV4-televised event.