SUZUKA, Japan - Red Bull's Mark Webber clocked the fastest lap in Saturday's final free practice for the Japanese Grand Prix as team mate and runaway championship leader Sebastian Vettel watched on in a pair of jeans.Vettel, who can clinch his fourth successive Formula 1 World title at Suzuka on Sunday, retired early after locking up his front left wheel and immediately returned to the garage.QUICK TIMESWebber clocked 1min32.053seconds to top the time sheets before the afternoon's qualifying. Lewis Hamilton was second quickest in 1min32.187 with McLaren team mate Nico Rosberg close behind in third. Ferrari's Fernando Alonso, a distant second behind Vettel in the standings, clocked the fifth fastest lap of 1min32.800.Vettel, winner of the last four races, recorded the ninth fastest time of 1min33.036 on hard tyres before encountering a KERS problem, raising the chances of a closer qualifying than anticipated given the German's rampaging form.Vettel, who did not get a run on the medium tyre, radiod to his team: "Locked up the front left. Just a little flat spot. Obviously it's not great."A victory in Sunday's race, combined with Alonso failing to make the top eight, will make Vettel only the third man to win four F1 titles in a row. After another win in South Korea last weekend, he has a massive 77-point lead with only 125 up for grabs from the last five races.