Belgian rookie Remco Evenepoel retained his lead but lost 48 seconds on key Vuelta a Espana rival Primoz Roglic on Saturday as Richard Carapaz bagged a gruelling stage win.

Carapaz was the sole survivor of a long-range escape on the 160km stage 14 to claim his second win of this Vuelta, but the day's main drama unfolded behind him heading towards the summit finish.

The final ascent in the Sierra Nevada was described as "hell" by former champion Alberto Contador, and at a section where a roadside sign read 15 percent incline, three-time defending champion Roglic attacked.

In sizzling Andalusian temperatures Evenepoel coolly watched the Slovenian pull away from him and rode on stubbornly at his own pace for the final 3km, crossing the line almost a minute adrift of the Jumbo rider.

"Today I didn't have my best legs. I couldn't accelerate when Roglic went. I'm still ahead, there's nothing to worry about," said Evenepoel.

"I just hope that that was my worst day of the 21."

The 22-year-old Evenepoel retains a 1min 49sec lead on Roglic with a similar stage on Sunday on a weekend of climbing.

Enric Mas of Movistar, third overall, and 21-year-old Carlos Rodriguez, fourth, both finished 20sec ahead of Evenepoel.

Sunday's stage 15 takes the Vuelta to its highest altitude at 2512m above sea level where the thin air can play havoc with a rider's performance.

The finale is a 19.5km uphill slog with around 7.5 percent average gradient.

Jay Vine, wearing the King of the Mountains polka dot jersey, has been decked out in matching spotted socks and shorts to go with it.

On Saturday, the 26-year-old Australian also raced on a polka dot bike, and retained his lead in the mountain points.

Denmark's Mads Pedersen retains the sprint points green jersey a day after his stage win.