Horner: Vettel now Alonso's only rival

Christian Horner believes this year's World Championship is now a two-horse race between Fernando Alonso and Sebastian Vettel.

The Red Bull team boss saw his man Vettel cruise to victory in the Japanese Grand Prix to move within four points of Alonso at the top of the standings, after the Ferrari driver was eliminated in a first-corner crash.

"We need to keep trying to get performance out of the car, and the championship now is effectively a battle of five races between Fernando and Sebastian," he said.

While it is close between the pair in the championship, there are four other drivers still in the title hunt in the shape of Kimi Raikkonen, Lewis Hamilton, Mark Webber and Jenson Button.

But with time running out for the other contenders to catch up, Horner believes it is a straight shootout between Alonso and Vettel for the crown, and insists he remains wary of the threat posed by Ferrari, despite Red Bull's dominance at Suzuka.

"You can't rule out the others but whoever does the best job over the next five races will ultimately prevail," he added. "I think that Fernando is a very shrewd and formidable opponent and over a season luck tends to balance itself out.

"Sebastian has had two DNFs because of reliability, Fernando has been unlucky with (Romain) Grosjean at Spa and with his puncture here.

"Luck tends to balance itself out over a 20-race season and it will be down to what the two of them do on track now and the relative performances of the cars over the remaining five races."

Horner was also keen to play down the significance of the 'Double DRS' device the team have used in recent races in an effort to improve straight-line speed, as their Renault power plant lacks the grunt of the Ferrari and Mercedes units used by their rivals.

He said: "As with all these things, there's never a silver bullet and I think it would be very difficult to say the car's performance here was purely down to a rear wing."