The 29-year-old Spaniard claimed the Spanish Vuelta on Sunday by being the most consistent rider during the 21-stage race that began Aug. 29 in Assen, Netherlands.
"I was missing a big win and now this year I've done it, it's incredible," the Caisse D'Epargne rider said. "I've proved to myself I can win a three-week event and I don't think any race, a Giro d'Italia or a Tour de France, can be much more difficult than this Vuelta."
The Vuelta, Giro and Tour are considered cycling's Grand Tours.
"If I've won here I think I can definitely be in contention for a Tour," said Valverde, who didn't compete in this year's Tour because it passed through Italy, where he was banned from riding because of a doping controversy.