Astana won the Giro with Vincenzo Nibali last month and decided to debut 25-year-old Sardinian Aru in the Tour this year. This week he is racing the Critérium du Dauphiné in France as his final lead-up event.
"What's difficult for him is the approach and the first stages of the Tour, there's so much more stress in those days, more than at the Giro d'Italia or the Vuelta a España," Trainer Maurizio Mazzoleni told Cycling Weekly.
"It's enough to have one particular moment to lose time, or gain time. That tension in the first stages could be the only difference for him compared to the Giro."
Nairo Quintana (Movistar) effectively lost the Tour last year to Chris Froome (Team Sky) when he missed a split due to a crash in the wind-swept second stage through the Netherlands and finished 1-28 minutes behind.
That same tension probably did not help team Froome in 2014, when he crashed three times in the first week and abandoned.
Watch: Critérium du Dauphiné essential guide
This year's Tour, July 2 through 24, cuts south from Normandy with what should be four tense stages until the classification will have a good shake in the fifth stage to Le Lioran. Aru, who has never raced the Tour and rarely races in France, could stumble on one of the early hurdles.
"I'm confident in him. It's his first Tour, but he's raced five Grand Tours – he has experience,” Mazzoleni added. “He's already faced off with Froome and Contador in the 2014 Vuelta. However, he's not completely mature yet, so I still can't say what's possible. Every year he's improving."
Aru debuted in the three-week Grand Tours with a 42nd spot in the 2013 Giro won by teammate Nibali. Since, he has never finished out of the top five: third in the 2014 Giro, fifth in the 2014 Vuelta, second in the 2015 Giro and winner of the 2015 Vuelta.
"He needs race days to get to the Tour, we calculated with the team that the last week of the Tour is the most demanding and also this year, he's aiming for the Olympics a week after the Tour," Mazzoleni said.
"It's important to be ready for the third week of the Tour. We calculated his training off of that, and we will still adjust it in the next two weeks. It's all based on him having the best possible lead-up.
"In the Tour of Poland before the Vuelta, it was the same. He rode a good time trial, but he was dropped on a stage. He didn't score a great result. Or ahead of the Giro, the same, and he placed second."
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