- Sebastian Vettel crashes during practice ahead of Japanese Grand Prix
- Red Bull's Vettel recovered to post third-fastest time, behind Jenson Button in first
- German Vettel needs one point in Japan to claim second successive drivers' title
- Ferrari's Fernando Alonso completed the top three
Sebastian Vettel needs just one point at Sunday's Japanese Grand Prix to claim a second successive Formula One world championship, but the Red Bull driver's weekend got off to the worst start possible as he crashed in Friday practice at the Suzuka circuit.
The German hit the tire wall on an area of the track known as the Degner curve but recovered to post the third-fastest time overall, with McLaren's 2009 title winner Jenson Button setting the pace with a lap of one minute and 31.901 seconds.
Button is the only driver who can still mathematically stop the 24-year-old becoming the sport's youngest double world champion, but the Briton would need to win the year's five remaining races without Vettel claiming a single championship point.
Vettel heads the standings with 309 points going into the season's 15th grand, 124 points ahead of second-place Button on 185.
Ferrari's Fernando Alonso, the Spaniard who Vettel would replace as the youngest two-time winner of the drivers' crown, went second-fastest with a time of one minute 32.075 secs.
"It wasn't a big mistake this morning, but in that moment I wasn't 100 percent awake and mistakes around here can be quite costly," Vettel told Formula One's official website.
"It wasn't a big impact, but it did some damage to the car, so it wasn't perfect. It did affect our run plan a little, but we had a solid afternoon.
"The circuit seems pretty tricky this year on these tires, they make the cars seem more alive, so Sunday will be an interesting race."
Alonso, 30, was positive following the two sessions and hoped to be able to keep pace with Red Bull and McLaren at the head of the field.
"We hope to be able to fight with McLaren and Red Bull," said Alonso, who is currently third in the drivers' standings behind Vettel and Button. "But we know it won't be easy. What we can say is that the feeling from today is a little bit more encouraging than in previous races."
Vettel's Red Bull teammate Mark Webber went fourth fastest, ahead of seven-time world champion Michael Schumacher for Mercedes.
Button's fellow McLaren driver and 2008 champion Lewis Hamilton endured a frustrating Friday, matching his teammate for pace in the first sector but not around the remainder of the circuit as he languished in eighth position.
The drivers will take the track for qualifying tomorrow ahead of Sunday's race, where Vettel knows a finishing position of 10th or higher will seal world championship glory.