"Fabio's talented and deserves his space and my schedule will also take into consideration his," Nibali said.
"The possibility of racing both the Giro and Tour exists, but you can't take them both on in top condition. My heart says 'Giro' but my head tells me 'Tour.' If I did race the Giro, though, I'd go to win it."
Nibali took the Tour de France lead early in Leeds, saw rivals Alberto Contador and Chris Froome abandon and won by 7-37 minutes over Jean-Christophe Peraud (Ag2r La Mondiale).
Italian fans want to see him return to the Giro, where he won already in 2013, but they may have to wait. Team Astana could send 24-year-old Aru, who won the Montecampione stage and placed fifth overall in 2014, to lead the Giro and Nibali to defend the Tour title.
The plan would exclude Nibali from participating in Tinkov's Grand Tour challenge. The Russian businessman and owner of team Tinkoff-Saxo with Contador said that he would give cycling's top four Grand Tour riders – Contador, Froome, Nibali and Nairo Quintana – €1m if they race all three Grand Tours in 2015. They could fight for the prize or split it to €250,000 each.
Contador already announced that he will race the Giro and Tour in 2015. If the others agree, he would likely race the Vuelta because Tinkov is his boss. Sky and Movistar both said that they would consider the ideas with their riders Froome and Quintana, respectively.
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Sky General Manager David Brailsford said, "It's quite a serious undertaking, but from a fans' point of view, from a sporting point of view, I think it's [Tinkov's idea] got a lot of merit."
Nibali, though, brushed off the idea and said that Tinkov is seeking attention. He told Italian website Tutto Bici last week, "To put down one million euro is just a way to make yourself look good."
Racing the Giro d'Italia in May, the Tour de France in July and the Vuelta a España in August/September, explained Nibali, would not be "humane" and would require a him to miss other races.
"These races all rest in your head and legs," Nibali told La Gazzetta dello Sport newspaper in an interview today.
"You'd have to cancel the rest, races like Tirreno-Adriatico and the classics... It'd just be race and training camp, race and training camp, race and training camp... And your family? When would you see them?"
Nibali said that he will confirm his 2015 schedule in November when he meets with Astana at its first training camp for the new season.
