Formula One: Mercedes boss had "a few words" with Hamilton

Mercedes team chief Toto Wolff admitted on Friday that he had "a few words" with world champion Lewis Hamilton about his recent behaviour. But, he said, it was not "a headmaster kind of discussion" -- just a couple of conversations to keep him on track after the Snapchat media furore that blew up in Japan. "I think we all underestimate the pressure that these guys are under and go through at these times," Wolff told reporters at a news conference for team bosses after Friday's practice sessions at the United States Grand Prix. His championship-leading Mercedes driver Nico Rosberg was fastest ahead of Australian Daniel Ricciardo of Red Bull with defending three-time champion Hamilton back in third. "When they come to the last few races and the whole season depends on the outcomes, it is big pressures on them," said Wolff. "Lewis feels it and he is very sensitive for the team. He knows there is a job to do inside the car and another job outside the car. It was a very tense weekend for him in Japan after what happened in Malaysia, where he lost a win." Wolff also admitted that he had never experienced such a task as that of managing Hamilton before. "He is a global superstar -- an exceptional individual in every aspect," he said, adding that he had to take him as he is including a few tantrums. "That is all part of Lewis. He has misjudged a few things, like in Japan, but he never meant to undermine anyone in the team. He is actually a very considered person. "I take him as he is and, actually, I think he has his heart in the right place." He also admitted that he believed Rosberg had raised his game to new levels this year and was more disciplined than ever. "He doesn't read a news article that is bad for him because it would annoy him," he said. "He just hides everything away that might distract him. He doesn't wear his heart on his sleeve, because he's so disciplined. I don't see the real Nico very often."