Oscar Rodriguez climbed to his maiden Grand Tour stage victory on a day that saw Jesus Herrada forced to fight hard to retain the lead at the Vuelta a Espana.
As the race moved into the mountains for the first of three tough days of climbing, Spaniard Rodriguez launched a solo attack on the ascent to La Camperona in the closing kilometre of stage 13.
Neither Rafal Majka - who crossed the line 19 seconds behind the winner - nor Dylan Teuns were able to keep pace, leaving them to fight it out for second place.
Bora–Hansgrohe's Majka won that battle at the end of a gruelling 175-kilometre ride from Candas that looked set to see a new race leader crowned.
Nairo Quintana was the first of the leading names to cross the line in 21st place, with fellow general classification contenders Simon Yates and Alejandro Valverde not too far behind the Colombian.
However, having taken over top spot from Yates with a strong ride on the previous stage, Herrada had enough left in his legs to maintain some of his advantage, coming home in 44th to at least secure one more day in red.
THE HEAT IS ON
Herrada's desperate push sees the Cofidis rider sit one minute and 42 seconds ahead of the rest - but for how much longer will he hold top spot?
Yates is the closest challenger but he has Quintana breathing down his neck after the Movistar man flexed his muscles with a strong burst on the final climb.
His efforts only claimed a few seconds over the Brit but suggested he has both the strength of mind and the stamina in the tank to make a move over what could be a crucial weekend in this year's race.
Meanwhile, fifth-placed Miguel Angel Lopez came to a standstill at one stage near the end due to a mechanical problem, though he made up for lost time and finished only three seconds behind Valverde and Thibaut Pinot.
1. Oscar Rodriguez (Euskadi-Murias) 4:17.05
2. Rafal Majka (Bora-Hansgrohe) +0.19s
3. Dylan Teuns (BMC Racing) +0.30s
4. Bjorg Lambrecht (Lotto Soudal) +0.38s
5. Laurens De Plus (Quick-Step Floors) +0.43s
1. Jesus Herrada (Cofidis) 54:50.19
2. Simon Yates (Mitchelton-Scott) +1.42s
3. Nairo Quintana (Movistar) +1.50s
1. Alejandro Valverde (Movistar) 85 points
2. Peter Sagan (Bora-Hansgrohe) 83 points
3. Benjamin King (Team Dimension Data) 68 points
King of the Mountains
1. Luis Angel Mate (Cofidis) 64 points
2. Benjamin King (Team Dimension Data) 40 points
3. Bauke Mollema (Trek-Segafredo) 34 points
Stage 14 sees the riders travel 171km from Cistierna to Les Praeres de Nava, taking in four intermediate climbs before a steep incline to the finish with an average gradient of 12.5 per cent.