Keegan Brown said he was "jumping for joy" after beating former world champion Raymond van Barneveld at the Grand Slam of Darts.
The 22-year-old, who is the PDC world youth champion, led 9-3 and almost surrendered his lead before sealing a 10-7 victory over the Dutchman.
Brown, from the Isle of Wight, is through to a quarter-final against Dave Chisnall in Wolverhampton on Friday.
"It's hard for me to describe," Brown told BBC Radio Solent.
"Van Barneveld is probably the second greatest player ever behind Phil Taylor. I'm absolutely over the moon."
Brown works as a medical lab assistant and has had to take holiday to feature in the Grand Slam, which features players from the PDC and BDO circuits.
He continued: "The thing with 'Barney' and the rest of the Premier League players is that you need to come out of the blocks firing.
"I raced into a 7-3 lead. Then he started playing like he can do so I became a bit twitchy. I told myself to focus and when I hit the bullseye I was jumping for joy. I'm just happy to get the win."
Brown has already earned a minimum of £15,000 for reaching the quarter-finals which is the biggest pay-day of his career to date and added: "I've played Dave (Chisnall) in the group stages, I'm playing well and am relaxed for that game.
"In all fairness, I've beaten seven years worth of world champions (following a group-stage win over 2011 and 2012 world champion Adrian Lewis) so I've got nothing to lose now."