The Dutchman from Maastricht has confirmed that he will be racing the Giro, which runs from May 4 to 27 and includes a high number of time trial kilometres than the Tour, after winning ahead of Nairo Quintana (Movistar) and Vincenzo Nibali (Bahrain-Merida) in 2017.
Chris Froome (Team Sky) has already confirmed that he will race both the Giro and Tour in 2018, and Dumoulin, too, could attempt the double. However any decision on Dumoulin's participation in the Tour will come after the dust has settled on the final stage in Rome.
"In my eyes a lot of riders have made the mistake in the past by focusing on both the Giro and the Tour from the start of the season," Dumoulin told Dutch newspaper De Telegraaf.
"As a result, they were probably already in the Giro with the classification in the Tour in mind. That is a mindset that does not work. I think you should focus completely on the Giro and only then have to look further."
Dumoulin spoke at the German WorldTour team's presentation on Thursday in Berlin. Wilco Kelderman, who announced he renewed his contract until 2020, confirmed that he would race the Tour and Vuelta a España. He could slot into a helper role at the Tour, saying he will take a serious crack at the Vuelta overall from August 25 to September 16 after finishing fourth in 2017.
Watch: Tour de France 2018 route guide
Instead, Dumoulin will focus on winning the Giro with its opening 9.7-kilometre time trial in Jerusalem and a 35.5-kilometre test in the third week providing plenty of opportunities for the world time trial champion.
Froome, according to Cycling Weekly sources, will receive a €1.4-million start fee for the Giro d'Italia. The amount is due to come from the Israeli organiser. Dumoulin, according to one insider, will also be paid.
Dumoulin, however, says otherwise. On Thursday, he explained, "I won't receive one euro of start money."
"Like every team, we receive a fee," Team Sunweb general manager Iwan Spekenbrink said. "It's by no means close to the amount mentioned with Froome."
With the Giro complete, Dumoulin could turn his attention to a crack at the Tour title for the first time.
"That is indeed an option for me next summer," he said. "I think it is not impossible to combine those two tours. Certainly so because there is a week extra this year because of the [FIFA] World Cup, which offers more possibilities."
If Dumoulin does not race for the Tour' general classification, he said that he would go for stage victories as he did in 2016 when he won the time trial and a mountain stage in Andorra. Otherwise, he could support Kelderman at the Vuelta or skip both the Tour and Vuelta.
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