Red Bull team principal Christian Horner says achieving a "quadruple double" would be a stunning achievement but is steadfastly refusing to take anything for granted in the race for Formula One's world titles.

With much of the Indian Grand Prix focus on Sebastian Vettel's bid to become only the fourth four-time champion in the sport's history, it has been easy to overlook the fact that his Red Bull team are also on the brink of the fourth title in as many years.

With four rounds left, Vettel enjoys a 90-point lead over Ferrari's Fernando Alonso while Red Bull are 148 points clear of the Scuderia in the race for the constructors' crown.

In view of Vettel's recent run of five straight wins dating back to the summer's Belgian Grand Prix, the general consensus is that it is only a matter of time before Red Bull can start popping champagne corks.

Horner, however, is holding off until every last shred of doubt has been removed.

"Should we achieve a quadruple double championship it would be an amazing feat for every single member of the team to achieve such results against such illustrious opposition, but those thoughts aren't really on our mind at the moment - our focus is very much on this event," Horner said after seeing Vettel finish fastest in both of Friday's practice sessions.

"The championship tables obviously look very healthy but it's never done until it's mathematically impossible for anybody else to win.

"The whole team's focus is very much on getting the most out of this weekend and the championships take care of themselves."

Paddock speculation suggests the team have already printed off T-shirts ready to celebrate tomorrow, but Horner warned: "If there are any T-shirts, I certainly haven't seen any and they'd be wise to keep them away from me."

The title victory would put Vettel in an elite group comprising Juan Manuel Fangio, Alain Prost and Michael Schumacher.

Vettel's team-mate Mark Webber was second quickest in both of yesterady's sessions, the gap between the two men growing from just under two-tenths to a shade under three.

The in-form Romain Grosjean was third for Lotus, half a second clear of team-mate Kimi Raikkonen, while Lewis Hamilton was seven-tenths off the pace in fourth, with his Mercedes team-mate Nico Rosberg sixth.

Alonso, the only man who can still deny Vettel the title, was in fifth place after recovering from a gearbox problem that saw him complete just six laps in opening practice.

McLaren's Jenson Button was 10th with Paul Di Resta 15th for Force India, while Marussia's Max Chilton once against propped up the pack.