Pre-tournament favourite Luke Littler fell to a 2-1 defeat by Rob Cross on his debut in the World Grand Prix in Leicester.
Teenage star Littler made six maximums in the match but at times struggled to get going in the double-start format despite levelling at 1-1 after losing the first set.
Cross impressively held his nerve against the 17-year-old, finishing with a bullseye in the fourth set to claim only his third victory in the tournament.
Englishman Cross, who won the World Championship on his debut in 2018, will now face Germany’s Martin Schindler in the second round on Wednesday.
Meanwhile, reigning champion Luke Humphries fought back from a set and two legs down to beat Masters winner Stephen Bunting 2-1.
Bunting won the first five legs against the world number one but missed a double 16 to win the match and watched on as Humphries took the next three legs to level, before pulling clear.
Humphries, who celebrated his maiden TV ranking title with victory over Gerwyn Price 12 months ago, is aiming to bidding to become the third player to retain it after Phil Taylor and Michael van Gerwen.
He now plays Germany’s Ricardo Pietreczko, who defeated Dutch five-time world champion Raymond van Barneveld 2-1.
In Monday’s other results, Nathan Aspinall defeated Ryan Searle 2-1, Schindler beat Brendan Dolan 2-0 and Ryan Joyce, Jonny Clayton and Ross Smith triumphed by the same scoreline against Josh Rock, Ritchie Edhouse and Gian van Veen, respectively.
