SUZUKA - Four-time defending world champion Sebastian Vettel on Saturday announced his shock departure from Red Bull and looked set to join Ferrari in a day of major upheaval in Formula One. Vettel won all his world titles with Red Bull in a four-year spell of dominance, but he will leave at the end of this season and be replaced by Russian rookie Daniil Kvyat, 20. "I have decided to leave Red Bull at the end of this year," the 27-year-old Vettel said in a statement on his website. Team principal Christian Horner told reporters that Vettel had only announced his departure late on Friday, during preparations for the Japanese Grand Prix in Suzuka. "Obviously Ferrari have made him a very attractive offer," Horner said. "Of course it is a big step and hard to make such a decision," Vettel said. –AFP