Mercedes still worried a 'freak incident' could derail Lewis Hamilton's fifth title

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Mercedes team boss Toto Wolff says he is not taking anything for granted as Lewis Hamilton closes in on a fifth world title.

Hamilton can secure the championship at the next round in Austin if he outscores Sebastian Vettel by eight points. Mercedes has secured one-two victories at the last two rounds and a third in the U.S.A. led by Hamilton would be enough to ensure he wins the championship regardless of Vettel's results.

But Wolff is wary of celebrating too soon and is worried that a minor injury or technical issue could still change the course of the championship.

"Freak incidents happen everywhere," he said. "A DNF and the consequent bad result suddenly wipes off a large chunk of your points. I know from the public standpoint it doesn't look likely, but this is motor racing, it's a sport, anything could happen.

"I don't want to even think about him breaking a finger. Anything can happen in motor racing.

"I don't want to dwell to much about it, because this is bad karma too, so let's just get it done -- let's go to Austin, let's have a strong race weekend and then hopefully see the championship."

Hamilton's lead in the championship has accelerated with four consectutive victories at the last four races, but Wolff insists his team have not been focussing on the gap to Ferrari in the standings.

"I think what we're trying to do is really to look at ourselves. They had a very strong weekend in Spa-Francorchamps [the last race Vettel won], and we didn't perform as per the expectations that we have now.

"Since then we have continued to really try to optimise our package and do the best possible job on the car and in the car with the drivers, and that has proven as the right tactic.

"Somehow none of us are looking at where Ferrari is or how the championship goes; it's just aligning those weekends that eventually hopefully will lead to a situation where we say we have won it."