American Ben King, of the Dimension Data team, claimed his second stage win of the Tour of Spain on Sunday after riding solo to victory on stage nine.
Britain's Simon Yates (Mitchelton) took over the leader's red jersey from Frenchman Rudy Molard (Cofidis) following the 200-kilometre race to the ski resort of La Covatilla.
Yates now leads Spanish veteran Alejandro Valverde (Movistar) by one second in the overall standings ahead of Monday's rest day.
Nairo Quintana, also of Movistar, finished among the chasers to move up to third place overall at 14sec behind Yates.
Days after breaking his Grand Tour victory duck on the race, King laid the foundations for his second stage win when he broke free from an 11-strong leading group around 10km before the start of the final climb.
The American's bid looked to be hanging in the balance when Dutchman Bauke Mollema (Trek) launched an audacious bid to reel him in.
Starting the climb a minute and a half behind King, Mollema dug deep to haul himself to within 15sec of the 29-year-old American, who appeared to be tiring in the final kilometres.
But the road -- in the shape of flatter gradients -- came to King's rescue, handing the American respite and a chance to recover before the final push for the finish.
King was in disbelief as he crossed the line solo in triumph for the second time in a week.
"I've never suffered that much in my entire life, I’m still a little foggy in my mind, but I’m sure it will sink in soon what an accomplishment this is," said King after requiring several minutes to regain his composure.
"To get one stage win was a dream come true. I made winning a Grand Tour stage a major career goal, so today was really nice to show that first one wasn't a random thing."
Yates, meanwhile, has pulled on the leader's jersey at a second Grand Tour race for the second time this season.
"Of course I'm very happy to be here in the red jersey," said Yates.
"It's a bit of a surprise, but I'm happy. I was just trying to follow the best guys in the race."
Last June, the Englishman wore the pink jersey at the Giro d'Italia and looked to be on his way to a career-defining victory before collapsing on stage 19, prompting an attack by Chris Froome that earned the Team Sky leader overall victory.
With more than half of this race to come, Yates added: "I don't know what the plan is now. We have the rest day to sit down with the team and make a plan."
The Tour of Spain resumes Tuesday with a 10th stage held over 177 km between Salamanca and Fermoselle that should be decided by the sprinters.
Froome, the reigning Vuelta champion, has chosen to ride in the Tour of Britain instead with Tour de France winner Geraint Thomas.