Barring disaster in Sunday’s parade around the centre of Madrid, Froome, who now holds a lead of 2min 15secs over Nibali, will become just the third rider in history to win the Tour de France and Vuelta in the same year.
“What a way to end a massive three weeks of racing,” said Froome. “For me having completed the Tour-Vuelta double now it’s an amazing feeling.”
Home favourite Contador sealed a dream send-off by claiming the first stage win of the race by a Spaniard in a time of 3hr 31min 33sec for the 117.5km from Corvera de Asturias to Alto de l’Angliru.
A three-time former winner, Contador, 34, claimed his sixth career Vuelta stage victory as he distanced the race leaders at the start of the brutal climb up Angliru.
“There could be no better ending than this,” said an emotional Contador.
“This morning I was clear that this was my day, that I had to say goodbye in this way.
“There has been no better moment or place than this to say goodbye.”
However, he just missed out on climbing onto the podium as he moved up to fourth overall.
Russia’s Ilnur Zakarin leapfrogged Dutch rider Wilco Kelderman into third.
Froome was again well protected by his Sky team in the chasing group behind, before attacking himself two kilometres from the finish line to take third on the stage behind teammate Wout Poels.
“That was such a tough climb,” added Froome, who also shed a tear as he was embraced by his team at the finish line.
“We did everything to try and catch Alberto, but he was too strong today.
“Congratulations to him because to finish his career like this is beautiful.”
– Toughest race –
With the fifth Grand Tour win of his career, Froome will join Frenchmen Jacques Anquetil (1963) and Bernard Hinault (1978) as the only riders to win the Tour and Vuelta in the same year.
But the Briton is the first man to win both races since the Vuelta was moved to after the Tour in the racing calendar in 1995.
Froome has finished runner-up at the Vuelta on three occasions in 2011, 2014 and 2016.
But that wait has made the final reward all the sweeter after a gruelling three-week slog he described as the hardest race of his career.
“I have to say it’s probably the toughest Grand Tour I’ve ridden, this year’s Vuelta,” added Froome.
“Every day was something else. It’s just such a big relief to have now got to this point and I’m looking forward to getting to Madrid tomorrow.
“I’ve been trying for years and I’ve been second three times, so to win the Vuelta now is incredible.”
Nibali’s hopes of launching a challenge for the leader’s red jersey were undermined by a minor crash on a sharp descent before the climb to Angliru began as the Italian finished 34 seconds behind Froome in sixth.
“You have to acknowledge that the Vuelta is extremely hard and my legs were heavy by this stage of the Vuelta,” admitted Nibali, a winner himself back in 2010.
“With two kilometres to go, I couldn’t follow the pace of my rivals.
“On a stage where I fell on the descent from Cordal which meant I lost contact with the best riders, fortunately I didn’t lose the podium.”