Team Ineos' Egan Bernal took the leader's yellow jersey as the Netherlands' Antwan Tolhoek claimed his first career victory by winning the sixth stage of the Tour de Suisse on Thursday.
Colombian Bernal, riding without teammate and Tour de France champion Geraint Thomas after the Welshman pulled out of the race on Tuesday with an injury, took top spot in the overall standings from three-time world champion Peter Sagan.
Bernal, 22, had been in the top 20 since the second stage in Switzerland and underlined his potential to stand in for Thomas and Chris Froome, who was ruled out of the Tour de France after a devastating crash at the Criterium du Dauphine last week.
Jumbo-Visma's fresh-faced Tolhoek, 25, has appeared at all three Grand Tours but only clinched his maiden senior stage success after an arduous day highlighted by a tough last climb.
Bernal finished second, 17 seconds behind him despite his late efforts, and Frenchman Francois Bidart was third.
The lengthy final climb up to the resort of Flumserberg split the breakaway into numerous groups with Tolhoek, Lluis Mas and Patrick Bevin alone ahead.
Tolhoek dashed ahead, leaving Mas and Bevin behind with less than 5km to go as UAE Emirates' Rui Costa joined the dropped pair.
They were then overtaken by Ineos's Bernal with 2km left as the Colombian powered to chase down Tolhoek but to no avail.
Tolhoek turned the final corner and was seen with a proud smile on his young face as he glided over the finish line.
Friday's seventh stage heads 216.6km north from Unterterzen to San Gottardo with the Lukmanier Pass at 1915m altitude the biggest test of the day.