Spanish motorcycle rider Marc Coma blew his chances of a second successive Dakar Rally win yesterday when he lost his way in the desert, hit a tree and knocked himself unconscious.

The runaway leader was picked up by a medical helicopter just 57km into the 13th stage from Kayes to Tambacounda in Senegal, coming round at the bivouac before being flown to hospital in Dakar for further examination of a head injury.

Until then, Coma had looked a certainty for victory, enjoying a dominant lead with only one significant timed stage remaining to come today before tomorrow's largely ceremonial final stint at the Lac Rose in Senegal.

In the car category, Frenchman Stephane Peterhansel increased his lead over Mitsubishi team mate and defending champion Luc Alphand to 11 minutes and 15 seconds. Spaniard Carlos Sainz won the stage for Volkswagen.

Coma's troubles began when the KTM rider seemed most in command. The Dakar website said the Spaniard was seen to lose his way.

"Several minutes later, he hit a tree stump on a parallel track six km away from the ideal route and was thrown against a tree," the website reported.

"Marc is hurting a lot but he is okay," said Coma's team manager Jordi Arcarons. "He hasn't broken anything. He's going to have a series of medical examinations in Dakar and then Barcelona."

The Spaniard's exit left 2005 winner Cyril Despres, in the lead after starting the day almost an hour adrift of Coma. Despres won the stage and overall he is 35 minutes ahead of David Casteu with American Chris Blais in third place.