Yellow jersey contender Cadel Evans remains upbeat despite the unwelcome news that Silence team-mate Thomas Dekker has been ruled out of the Tour de France due to a positive doping control.

Dutchman Thomas Dekker has been ruled out of the Tour de France after a positive test for the banned blood-booster EPO, his Silence-Lotto team said.

Cadel Evans is determined to seize his chance to become the first Australian to win the Tour de France.

Australian Cadel Evans has been given scope for a more promising tilt at the Tour de France yellow jersey with a reinforced team for the July 4-26 event.

Spaniard Alberto Contador will be Astana's leader on the Tour de France, team manager Johan Bruyneel said.