Eurosport - Fri, 29 Aug 11:25:00 2008
"I want to see how well I can do, but that's as far as it goes," the leader of the Astana team told Reuters.
"I'd like to win it before I retire, but I'm only 25, I've got a lot more years of racing ahead of me.
"Also, I've never ridden the Vuelta before and that lack of experience could weigh against me. For now, I'm just one of the contenders for the overall victory."
Already victorious in the Tour de France 2007 and the Giro d'Italia in 2008, Contador's goal is to become the fifth rider and first Spaniard to win all three major Tours.
Contador missed out on defending his Tour de France title this year after Astana were barred from starting because of doping scandals in 2007.
Since beginning racing for the team earlier this year, Contador has won the Giro and also finished second in his most recent event, last weekend's Vuelta a los Puertos.
His biggest challenger is likely to be compatriot Carlos Sastre, who went on to win this year's Tour de France after taking a solo win on the infamous Alpe D'Huez climb.
"Taking part in the Giro and winning it was a really big achievement, bigger than if I'd had a second victory in the Tour de France," Contador said.
"Now in the Vuelta I want to enjoy myself, see what happens and do as well as possible.
"When I was an amateur, several times the race went past my house; back then, to me, if you took part in the Vuelta you were a professional.
"Just taking part in the Vuelta means a dream I've had since I was very young has finally come true."
He hoped the initial stages would help fine tune his form.
"I need to be in good shape for the Pyrenees at the end of the first week, but I have to be on top of my game for the Angliru climb [on stage 13]," he said.
"In my opinion, the Angliru is the most crucial stage of the whole race."
The Vuelta finishes in Madrid on September 21.