Sagan began his professional career with team Liquigas in 2010 before rising. Former Liquigas general manager Roberto Amadio said three years ago that he thought Sagan could one day win the Tour de France, comments that he stands by.
"And I still believe it," Amadio told Cycling Weekly.
"It's clear, he'd have to modify his body, thin down, losing power, everything, but I think he's taking advantage of his natural talents now. He's always giving a good show and pulling off wins.
"Working on it, he could also win a Tour de France designed in a certain way. He'd have to defend in the time trials and on the climbs... but it's a complex discussion. He'd have to be smart, like Bradley Wiggins, and make enormous sacrifices to modify his body."
The perfect storm for an improving Wiggins came in 2012. Tour organiser ASO presented a course that included two long time trial stages and a prologue adding to just over 100 kilometres against the clock. Wiggins won the two time trials and stayed with the best climbers in the mountains.
Watch: Pro Bikes of 2017 - Peter Sagan's Specialized S-Works Roubaix
If ASO went further in the direction of aggressive stages with cross-winds and technical or downhill finishes then Sagan could gain an advantage over some rivals.
"Yes, exactly, [he needs the course and] the head and body for it.
"He can go well on climbs [like in Tirreno-Adriatico's Fermo finish ahead of Thibaut Pinot, Geraint Thomas and Nairo Quintana] and he can go well in a time trial too," added Amadio.
"With four kilograms less and keeping some power, they'd have a hard time dropping him on the true climbs. But, it's an enormous sacrifice mentally and physically that I don't know if it's worth it."
Sagan has been world champion for the last two years and has concentrated on the big one-day races, taking the Tour of Flanders title last year and fighting, unsuccessfully, for victory in Milan-San Remo, Flanders and Paris-Roubaix this spring.
Alongside his Classics success, Sagan has also won the green jersey at the Tour de France for the past five years.
According to Amadio, the 27-year-old from Slovakia would need to consider soon if he wants to develop into an overall classification contender.
"If he wants to race up until 32 or 33 years old, then he needs to do it [become a GC rider] when he's 29 to 32, when he's at his full physical best. That's the ideal age range for cyclists."
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