Simon Yates' Giro d'Italia challenge sprung to life on Saturday as the Briton emerged from the fog of the gruelling 14th stage climb to Monte Zoncolan as the main challenger to overall leader Egan Bernal.
Former Vuelta a Espana winner Yates, who was forced to retire from last year's delayed Giro after testing positive for Covid-19, had warmed up with a win on the Tour of the Alps.
And the Team BikeExchange rider pulled out his strongest performance on the first real mountain test in the fog and cold of the Carnic Alps straddling Italy and Austria.
Italy's Lorenzo Fortunato of Eolo-Kometa claimed his maiden win 26sec ahead of Slovenian Jan Tratnik with Italy's Alessandro Covi nearly a minute off the pace.
Behind, among the overall race favourites Yates, 28, attacked inside the final two kilometres with only pink jersey wearer Bernal of Ineos able to follow.
The Colombian pulled ahead of Yates over the top in the closing metres, to cross the line 10 seconds ahead of the Briton in fourth.
Yates held off other rivals to cross in sixth and now sits one minute 33 seconds behind the 2019 Tour de France winner with seven stages still to come.
"It was good today, I had better legs than the first week and I am slowly getting there so I am happy with where I am at," said Yates.
"Bernal is the man to beat, he obviously showed he had great legs again today, it is going to be tough to beat him, but we will try.
"I hope to have the same legs as I had today for the rest of the race now and hopefully, we can try something and try to take the jersey."
- 'More rivals than guy in second' -
Aleksandr Vlasov had been second at the starting line at Cittadella but dropped to fourth overall as his Astana team lost steam in the final 7km leaving the Russian isolated.
Britain's Hugy Carthy, French climber Romain Bardet, and Belgian Remco Evenepoel also lost out on the day.
"There is still a long way to go until Milan, but the Giro d'Italia started this afternoon," said Yates' BikeExchange team sport director Matt White.
"It was the first day of a tough three-day block and we have made up some good time on our rivals and we are in a good place."
Bernal extended his overall advantage as he competes for the first time in the race around Italy.
"Now I have a good lead but I need to remain calm and focused, anything can happen in the Giro," said Bernal.
"I always said I had more rivals than the guy in second place behind me. It was Remco (Evenepoel), then Vlasov and now it's Simon Yates.
"I expected Yates to do so something today. It was a very good stage for him. He looked strong. I'm sure he'll remain one of the strongest."
Former two-time winner Vincenzo Nibali, whose build-up to his home race had been hampered by a fractured wrist, slumped to now nearly quarter of an hour adrift.
"I don't have the legs and I've no idea how the Giro is going to turn out for me," said the 36-year-old Trek-Segafredo rider.
Sunday's 15th stage covers 147km from Grado to Gorizia, in the north-east, crossing into neighbouring Slovenia before finishing back in Italy.