Ireland's Nicolas Roche slipped back to sixth position at the Vuelta a Espana as horrendous weather conditions hit stage 14 of the race from Baga to Andorra-Collada de la Gallina.

Roche came home in 20th position, over seven minutes behind stage winner Daniele Ratto of Italy, with compatriot Vincenzo Nibali finishing second to extend his lead in the general classification standings. Roche is now four minutes and six seconds adrift of Nibali's lead.

Cannondale rider Ratto battled against cold temperatures and rain in the mountains to record his first victory as a professional, finishing in a time of four hours and 24 minutes for the 156-kilometre stage.

Nibali finished three minutes and 53 seconds further back having stayed on the wheel of Chris Horner, with the holder of the red jersey then overtaking the American in the final metres of the race to finish second.

That helped the Italian increase his overall lead to 50 seconds, with Horner now his closest challenger and Spain's Alejandro Valverde one minute and 42 seconds adrift in third.

Ivan Basso, who was seventh before Saturday's stage, was forced to retire from the race on the Envalira descent, with his Cannondale team confirming the 35-year-old was suffering from hypothermia.