Krzysztof Ratajski missed six match darts as debutant Nathan Rafferty reached the last 16 at the Grand Slam of Darts.
After eight legs went with the throw, Rafferty capitalised on some nervous mistakes from his vastly more experienced opponent to break at the death.
It means he takes second place in Group A behind Gerwyn Price, who beat Rafferty in a decider on Saturday. The youngster is rewarded with a clash with Jonny Clayton later in the week.
"Words can't describe what I'm feeling right now, it's completely mad," said Rafferty, fortunate to witness Ratajski spurn several chances to seal a 5-3 win and then another in the final leg, but ruthless with his own match dart.
Rafferty joins Bradley Brooks in the knockout stages, both 21-year-olds helping to showcase the depth in darts.
"We're two people who've qualified out of the youth tour, and we're last 16 - that says enough," he said, addressing criticism as to the qualification criteria.
Earlier, Brooks had seen off Rusty-Jake Rodriguez 5-3 to follow Clayton through in Group B.
Brooks missed 18 attempts at double but can forget all about that now and prepare for his last-16 encounter with Price, who lost 5-4 to Martin Schindler but had already sealed top spot.
Clayton meanwhile won 5-4 against Mervyn King, who perhaps should've won the game having more than matched the in-form Welshman.
Group C concluded with James Wade beating Rob Cross 5-2, the latter just scraping his way to the legs he needed to avoid being overtaken by Jim Williams, a 5-1 winner against Boris Krcmar.
Stephen Bunting meanwhile suffered a 5-1 defeat to Rowby-John Rodriguez, who averaged closed to 105 and hit five from seven doubles in an impeccable, coming-of-age display.
Bunting can count himself unlucky having lost twice this week to averages of 105 and 108, falling to bottom of a group topped by Ryan Joyce despite his closing 5-3 defeat to late addition Chris Dobey.
Monday November 15 (7pm)
TV Coverage: Sky Sports
Group Matches (Best of 9 legs)
Group A
Group B
Group C
Group D
Groups E-H to be completed on Tuesday - schedule information here