Horner: Bad year made Sebastian Vettel better

Vettel was soundly beaten by new Red Bull team-mate Daniel Ricciardo this season, failing to win a race for the first time since he became a full-time F1 driver in 2008.

The German decided to leave the Milton Keynes squad with a year left to run on his contract, opting to seek a fresh challenge by replacing McLaren-bound Fernando Alonso at Ferrari.

Horner said a tough final season at Red Bull, in which Vettel found it difficult to get comfortable with the handling of the RB10, would ultimately be good for his former charge.

"I think it was a very difficult year for him - a character building year, in many respects," Horner told AUTOSPORT.

"He's had a lot of bad luck and things didn't go his way more often than not.

"On top of that, he was not happy in the car with the regulation changes from 2013 into 2014.

"He's a tremendously talented guy and I think it's the first time he's had a team-mate who has challenged him as well.

"Again, that is a different dynamic that he's had to deal with [because] he's always had team-mates covered in the past.

"It's been a difficult year, but not once has he let his chin drop or kicked the team.

"I think ultimately he'll take away a lot of valuable lessons from this year."

Horner said Red Bull would feel the loss of Vettel, who won 38 times in 113 starts for the team between 2009 and '14, but hoped emerging stars Ricciardo and Daniil Kvyat - who will replace Vettel at Red Bull next year - would fill the void.

"Obviously a driver of his calibre and the amount of success that we have enjoyed together; it will be a real shame to see Sebastian leave," Horner added.

"But we can be hopefully comfortable in the knowledge that Ricciardo - he is a fantastic talent and we've seen how he has performed head-to-head with Sebastian this year - with an exciting new talent in Kvyat means the future is very bright for us."