The Formula One title battle is turning into a straight duel between Ferrari's Fernando Alonso and Red Bull's Sebastian Vettel for the honour of becoming the youngest triple world champion.

By winning Sunday's Japanese Grand Prix after Alonso had spun off at the start, 25-year-old Vettel slashed the 31-year-old Spaniard's lead to four points with five races -- a maximum 125 points -- remaining.

Finland's 2007 champion Kimi Raikkonen is third for Lotus but 37 points off the lead and has yet to win a race this season while McLaren's Lewis Hamilton is fourth a further five points adrift.

Red Bull team principal Christian Horner refused to rule out McLaren, winners of five races this year, and Lotus but he also spelled out where the real challenge lay for the champions.

“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,” he told reporters.

Vettel has suffered two alternator failures and not scored on three of his races, while Alonso has twice drawn a blank -- both coming in the last four outings and due to first lap incidents beyond his control.

Raikkonen is where he is because of consistency -- 12 races in a row in the points -- while 2008 champion Hamilton and his car have been quick but erratic.

“The championship now is effectively a battle of five races between Fernando and Sebastian,” said Horner. “You can't rule out the others but whoever does the best job over the next five races will ultimately prevail.”

After the first seven races of the season were won by an unprecedented seven different drivers, the championship has settled into a familiar pattern with the focus on Ferrari, McLaren and Red Bull.

Vettel's commanding pole-to-flag triumph, with the fastest lap thrown in as well, at Suzuka made him the first driver this season to chalk up back-to-back wins and he joined Alonso and Hamilton as a three-times winner in 2012.

As in 2010, when the German became the youngest champion, the season appears to be coming good for Vettel at just the right time.

Alonso had led by 29 points before Suzuka but he could lose his advantage altogether when Formula One re-groups in South Korea for the 16th round of the season this weekend.

“I guess Fernando will be going home more unhappy than most, he is under pressure, more pressure frankly from Sebastian than from us but we have closed that gap and we have five races to go,” McLaren principal Martin Whitmarsh told reporters in the Suzuka paddock on Sunday.

“Red Bull were on form here and at the moment Ferrari are under some pressure from us and Red Bull,” added the Briton, who had Jenson Button fourth and future Mercedes driver Hamilton fifth on Sunday.

Ferrari president Luca Di Montezemolo expected his team to hold their nerve. “We know we can count on the strongest driver around at the moment and it's only mistakes from others at Spa and again at Suzuka that have prevented him from having a more comfortable lead over his rivals,” he said of Alonso on the team website (www.ferrari.com).

“But for those two collisions, today Fernando would have had at least 30 points more and that's a conservative estimate. In sport, as in life, the wheel turns and we must not forget that.”