Mark Cavendish has abandoned the Vuelta a Espana on the race's fourth stage.
The 26-year-old fell behind the main peloton on a tough category one climb at the start of the stage, and abandoned with around 40km to go.
The HTC-Highroad rider had struggled in hot weather on Monday and began Tuesday's stage to Sierra Nevada 16 minutes and 48 seconds off the leaders.
Cavendish, who won the sprinters' green jersey at the Tour de France in July, had yet to score any sprint points.
A team source said he was exhausted following the Tour de France and would now look to recuperate prior to the world championships in September.
The stage was won by Daniel Moreno who closed to within 43 seconds of overall leader Sylvain Chavanel.
Cavendish is the second HTC-Highroad rider to quit after Australian Matt Goss abandoned the race on its first day.
Cavendish, who won five stages in this year's Tour de France in taking his tally to 20, hopes to claim his first road race world title on 25 September in Copenhagen. Great Britain have qualified to enter a team of eight riders, one short of the maximum.