Four-time defending world champion Sebastian Vettel has announced his shock departure from Red Bull and looks set to join Italian rivals Ferrari, his team principal said Saturday.
Vettel, 27, won all his world titles with Red Bull in a four-year spell of dominance, but he will quit at the end of this season and be replaced by Russian rookie Daniil Kvyat.
Horner told reporters at the Japanese Grand Prix in Suzuka that Vettel announced he was leaving late on Friday, adding: "Obviously Ferrari have made him a very attractive offer."
A Red Bull team statement said: "Sebastian Vettel has advised us that he will be leaving Infiniti Red Bull Racing at the end of the 2014 season."
"We're pleased to announce that Daniel (Ricciardo) will be joined in the team for 2015 by another rising star from the Junior Programme, Daniil Kvyat," it added.
Vettel is currently fifth in the standings after a winless season in which he has been outshone by Australian team-mate Ricciardo's outstanding first year with Red Bull.
The Australian has won three races in Canada, Hungary and Belgium to sit third in the drivers' championship, behind Mercedes duo Lewis Hamilton and Nico Rosberg.
Vettel has totted up 38 wins and 44 pole positions with Red Bull as he became Formula One's youngest world champion and only the fourth driver to win four titles.
"We want to warmly thank Sebastian for the incredible role he has played at Infiniti Red Bull Racing for the last six years," the Red Bull statement said.