Daryl Gurney delivered a stunning performance, whitewashing six-time champion Michael van Gerwen in straight sets.
The Northern Irishman's clinical finishing and composure proved too much for the Dutchman – one of the tournament favourites – who was left stunned by the defeat.
"There's not many players that will beat Michael van Gerwen 6-0, but I won't get carried away," Gurney, who won the tournament in 2017, told the PDC website afterwards.
"I'm playing well, and I have been for the last couple of months.
"I have been beating players on the stage that I haven't beaten for a couple of years – Dave Chisnall, Nathan Aspinall, Gerwyn Price and now Michael, so that gives me a bit more belief."
Michael Smith and Peter Wright also suffered early exits.
World number two-ranked Smith was narrowly defeated by Gary Anderson in a thrilling match that went down to the wire. Wright, meanwhile, fell to James Wade 2-1 in a hard-fought contest.
Other notable results included Joe Cullen's comeback win over Chris Dobey and Gerwyn Price's dramatic victory over Danny Noppert.
The likes of reigning world champion Luke Humphries, Jonny Clayton, and Luke Littler-defeating Rob Cross step up onto the oche on day three on Wednesday, each looking to make a deep run in the tournament after positive starts.
Wednesday's matches:
Second round matches
Nathan Aspinall v Ryan Joyce
Rob Cross v Martin Schindler
Luke Humphries v Ricardo Pietreczko
Jonny Clayton v Ross Smith
Follow the Darts World Grand Prix action as it happens here.
