Ben Healy of Education First pulled off a long-range breakaway to win stage eight of the Giro d'Italia on Saturday, as race favourite Remco Evenepoel came under pressure.
The 22-year-old Irishman dropped his three breakaway companions on the day's hardest climb, the Monte Delle Cesane.
"I had great legs and nobody could follow me, so it was a great day," said Healy, who has broken through this year coming second to Tadej Pogacar in April's Amstel Gold Race.
Drama unfolded in the overall race as Primoz Roglic attacked Evenepoel.
While Roglic managed to drop Evenepoel, Ineos pair Geraint Thomas and Tao Geoghegan Hart also skipped past the Belgian as the trio managed to trim his advantage in the standings by about 15 seconds.
Evenepoel had come under criticism overnight for having returned to his hotel from an Apennine peak by helicopter.
Norway's Andreas Leknessund retained the overall lead ahead of Evenepoel while Roglic climbed to third.
Other fancied riders Damiano Caruso and Joao Almeida kept pace and Ineos pair Thomas and Hart seemed to have brushed off the loss of teammate Filippo Ganna who has Covid.
Leknessund is almost certain to lose his pink overall jersey on Sunday when the Giro stages its second of three individual time trials, a 35km run to Cesena.