Slovenian Tadej Pogacar mastered the mountainous Vuelta a Espana 13th stage on Friday with his compatriot Primoz Roglic consolidating his grip on the leader's red jersey.

The stamina sapping 166.4-kilometre ride featuring seven climbs saw Pogacar attacking on the brutal final 'hors categorie' ascent to Los Machucos.

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"It's an incredible day for me. I heard on the radio that no one was following me as I attacked. I realised it was a very good opportunity," Pogacar said.

While the 20-year-old (riding for UAE Emirates) was the day's winner, Roglic, who crossed the finish line in second, took a giant stride towards overall victory in Madrid on Sunday week.

He extended his lead over Alejandro Valverde at the top of the general classification to two minutes and 25 seconds.

"Today was a massive fight. It's a great day for Slovenian cycling," Roglic said.

Miguel Angel Lopez and Nairo Quintana, two other key challengers to win cycling's third Grand Tour of the year, are now trailing by 3min 18sec and 3min 33sec respectively ahead of the 14th stage after being left in Roglic's wake.

Pogacar is now third in the standings ahead of Lopez and Quintana at 3min 01sec.

The sprinters will be far more suited to Saturday's 188km ride with an anticipated mass sprint finish in Oviedo.

The stage should allow Roglic and his main title rivals to draw breath ahead of a return to the mountains on Sunday.