The Spaniard, 31, said his recovery from an early exit at the Tour de France saw him take his time to work into the three-week Vuelta.
The Tinkoff-Saxo leader pinpointed the 185-kilometre trek from Carboneras de Guadazaon to Aramon Valdelinares on August 31 as the moment he felt he could see off rival Chris Froome of Team Sky.
Froome ended up one minute 10 seconds behind Contador, with Spaniard Alejandro Valverde third a further 40 seconds back.
"The first day that I had a good feeling and I noticed I was doing well, was in Valdelinares," Contador said.
"That was maybe the day that marked the change in the race, up to that moment it had been difficult.
"I was lucky the team supported me incredibly in key moments, being with the wind, or finishing tough phases.
"So from there, and with Borja's time trial, my vision of the race changed."
Contador assumed the race lead following the 36.7km individual time trial in Borja on September 2, the 10th stage of the race.
His victory in Spain was all the more remarkable given he sustained a hairline fracture in his shinbone on stage 10 of the Tour de France.
Contador said he willed his way to victory.
"Well, I think of a phrase I always remember, 'Where there's a will there is a way'," he said.
"You think about a lot of people, experts too, who thought the recovery was tough.
"Since the first day I did everything I could to recover, the day after my fall we had a chiropractor from the team helping me because my muscles were sore from it.
"It's true I didn't think I would be able to fight for first place then, but luckily three weeks racing allows you to progressively reach the level you want, and that's what happened in this case."
Contador said competing in all three grand tours in 2015 was on the cards, even if he conceded it was only a "dream" at this early stage.
"It is early still to think about next year's calendar and big races, " he said.
"What I can say is that I'll be as dedicated as I was this year. [I'm] focused on obtaining my maximum performance on the bike from the beginning to the end of the season.
"I don't know what I can plan for next year. The truth is I have a dream, but many times I think of it with my heart.
"But after analysing the amount of things I'd have to do I don't really end up taking that step, that would be racing the three big races.
"I'd like to. But well, it's a dream, something really complicated. I think right now I can't think about that."