Red Bull continued their dominance in practice for the Indian Grand Prix, with their rivals admitting that they are “unstoppable” this weekend. Sebastian Vettel, who looks set to claim a fourth consecutive drivers’ championship on Sunday, was quickest in Friday afternoon’s session, 0.289 seconds ahead of teammate Mark Webber. As he was two weeks ago in Japan, Lotus’ Romain Grosjean was best of the rest in third. The only man who can still, mathematically at least, deny Vettel, the title, Fernando Alonso, was fifth, sandwiched by the Mercedes of Lewis Hamilton in fourth and sixth, respectively. Both Mercedes drivers thought that a place on the front row in qualifying was out of their grasp.

“Generally, it seems that the main question this weekend is who can get third position behind the two Red Bulls, because they look pretty unstoppable at this circuit,” Rosberg conceded, according to the official Formula One website.

Hamilton was similarly tempered in his aspirations. “We're working towards a strong qualifying performance tomorrow afternoon, ideally on the second row, and then hopefully a place on the podium, that would be nice,” he explained.

Vettel, who has won the past five races, holds a 90 point lead in the championship with just 100 more available from the final four races. But, despite being quickest in practice and winning for the past two years in India, the German was more concerned with the tire situation. Both Red Bull’s suffered from blistering of their tires when running the soft compound.

“The soft tire is not lasting so long here, but it’s Friday and the track is still rubbering in; it’s normally improving for Saturday, plus we haven’t used this compound for a long time, so tomorrow it should be better,” he said.

Alonso has struggled for pace in his Ferrari in recent races as he has attempted in vain to manufacture a genuine title challenge. The Spaniard does not expect things to be any different this weekend.

“The situation is not that different to recent races,” he said. “We are a bit behind in performance terms and tomorrow we must try and get a good starting position to get away well in the race and make it to the podium.”

Alonso’s teammate was seventh quickest in second practice, ahead of Kimi Raikkonen and the McLaren duo of Sergio Perez and Jenson Button.

The race in New Delhi was in jeopardy earlier this week with a hearing being called into allegations that race promoters had not paid taxes for last year’s event. Although this year’s event has been cleared to go ahead on schedule, the long term future of the Indian Grand Prix is uncertain with it not being included on next year’s Formula One calendar.

Where to watch: Qualifying for the Formula One Indian Grand Prix will get underway at 4.30 a.m. ET. Coverage will be provided by the NBC Sports Network, with a live stream available on NBC Sports Live Extra.