Oct.1 (GMM/Inautonews.com) Mercedes team boss Toto Wolff says he is taking Ferrari seriously as the Italian team continues its resurgence in 2015.

While Sebastian Vettel won dominantly in Singapore, Mercedes successfully ended its brief slump last weekend at Suzuka with a one-two.

Still, German Vettel is not giving up the fight for the championship, even though he trails Lewis Hamilton’s lead by 59 points with just five races to go.

“What kind of racing driver would I be if I stopped believing?” the Ferrari driver said.

According to Speed Week, Vettel’s continuing belief could get a boost in Austin later this month, when Ferrari trades in its final four upgrade ‘tokens’ for one last engine performance upgrade.

It is enough to make Mercedes’ Wolff very wary.

“Ferrari is marching forwards in leaps and bounds,” he told Germany’s Sport Bild.

“The speed with which they have done that is impressive, and we can expect another great leap in 2016.”

The Austrian agreed with Vettel’s view that Mercedes is still obviously superior, but “Whatever happens in the future, it is clear that what took place in 2014 will not be repeated”.

He is referring to last season, when Mercedes was not seriously rivalled by any other team. In 2015, however, there is the ever-improving Ferrari, ably led from the cockpit by Vettel.

“He (Vettel) has certainly had an influence,” Wolff admitted, “by motivating the troops but also because he has a great technical understanding and knows how to win races.”