Rodriguez, racing for the Katusha team, leads the Vuelta by 28 seconds from Spanish compatriot Contador, a double Tour de France winner regarded by many as the best stage racer in the world.
But Contador has failed to shake Rodriguez despite persistent attacks on the mountains, and only five days' racing remain before the tour finishes in Madrid on September 9.
"If I'm honest, if I seem so calm it's because I keep on expecting Contador to beat me," Rodriguez told reporters in his team's hotel during the rest day on Tuesday.
"Finishing second behind Contador wouldn't be like finishing a race behind Johnny Nobody, it would be a great achievement."
As for beating Contador, Rodriguez said: "It would be something very important. He's never lost a Grand Tour except the Tour de France in 2011, when he had a couple of bad crashes. Beating him would be something spectacular."
Rodriguez, 33, believes that after finishing second in the Giro d'Italia this May he has a strong chance of going one better in his country's biggest race.
"There are still two big mountain-top finishes (on Wednesday and Saturday), and that's why we've got to pay attention to the slightest detail," he said.
"In the last week of a Grand Tour there's always some dangerous situations, attacks when you least expect them, and the Bola del Mundo [summit finish on Saturday] could produce a surprise."
Rodriguez did not think Contador's morale was sapped by the fact he has been able to match his attacks throughout the race.
"I don't think so," he said. "He's still got his last card to play (the Bola del Mundo) and he's been in more difficult circumstances than this one. He doesn't have to feel bad, and I just hope I'm up to his level there."
Racing resumes on Wednesday with a hilly 187.3-kilometre ride from Santander to the summit finish of Fuente Dé.