A spectacular downhill mass attack by the Liquigas-Cannondale squad netted the team a stage win for Slovak all-rounder Peter Sagan and allowed Vincenzo Nibali to claw back time on Tour of Spain leader Sylvain Chavanel.

As the lead group of 40 riders tackled a well-surfaced but twisting descent at speeds of nearly 90 kilometres per hour, four Liquigas riders followed by Spain's Pablo Lastras sheared off the front.

Sagan powered across the line at Cordoba to claim his 12th victory of the season, with Lastras in second and Italy's Valerio Agnoli third.

The only favourite present in the lead group of five, last year's winner Nibali gained 17 seconds overall leader Chavanel thanks to his fourth-place finish.

"Ideally Nibali would have won and got some bonus seconds too, but I had to sprint to stop Lastras from taking the win," Sagan told reporters.

"In any case, it's a great day for the team, we got four out of the top five places, that doesn't happen very often.

"It wasn't a planned attack on that descent, we just thought we'd stay in front to avoid crashes and perhaps go for the stage for me.

"Suddenly, though, on the descent we realised we could go for it and open up some time on the overall as well as get the stage. It was like a team time trial."

The 21-year-old Slovak national champion said snagging his maiden win in his first major Tour was an important milestone in his career.

"I'm here to work for Nibali, who's got a great chance of winning this race, but this is a big moment for me too," he said.

"This is our first win in the Vuelta this year, and I'm hoping it won't be our last.

"My personal objective? To reach Madrid."

Sagan admitted attacking on the twisting 10 kilometre descent had not been without risks, while second-placed Lastras, a former race leader and stage winner, said he had "never been scared on a descent until today, and I've been a pro since 1998."

Chavanel continues to lead for a third successive stage, with Spaniard Dani Moreno at 15 seconds and Nibali moving up to third at 16 seconds.

The Frenchman should have an easier day on Friday's flat run over the plains of central Spain from Almaden to Talavera de la Reina.

The 2011 Tour of Spain finishes on September 11 in Madrid.