Red Bull team principal Christian Horner believes struggling through a difficult year in 2014 will have made four times world champion Sebastian Vettel better.
In his final year with Red Bull Vettel failed to win a single race while his team-mate Daniel Ricciardo won three. He has been with Red Bull since 2009, but the German decided to move to Ferrari ahead of the 2015 season.
Horner said: "I think it was a very difficult year for him – a character building year, in many respects.
"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."