Nico Rosberg thinks Sebastian Vettel needs to step back and reanalyse his mental approach to race weekends if he wants to beat Lewis Hamilton to the Formula One championship in 2019.
Vettel looked to be well placed for a fifth world title earlier this year but a series of mistakes have handed the initiative to Hamilton, who can wrap up the championship at Austin's U.S. Grand Prix this weekend. Rosberg beat Hamilton to the title in 2016 when the pair were teammates at Mercedes, before he retired at the end of that season as world champion.
When asked what it takes to beat Hamilton over a season, Rosberg told ESPN: "It's all about finding marginal gains. For me I realised that lots of little things can add up to a very big thing, if you get them all working the right way.
"[In 2016,] I was speaking to a psychologist, sometimes every two hours a day, and making sure that everything I was doing was perfectly focused on improving every little aspect of my performances. Every driver is different so he has to find his own way."
Although Vettel has made numerous errors this year, Rosberg thinks it can take only one to hand the initiative to his old teammate.
"The battle against Lewis is so tough because he is so tough mentally. If you don't get that right you aren't going to beat him. If you then start making mistakes as well, forget it.
"This season [for Vettel] has been a little crazy. He should be in the position to win the title right now and that's got to be tough to take for anyone, especially when the mistakes have been your own and not the team's. I don't know if this is the best Lewis has ever driven but when he's competing at the level we are seeing right now only a completely flawless performance is going to beat him most weekends and that's tough when you're on the back foot or you're worried about making more mistakes."
Rosberg was speaking at the announcement of Heineken's partnership with Formula E.