Defending champion Vincenzo Nibali said top rivals and a "terrible" third week of the Giro d'Italia will fully test him as he targets a third pink jersey in the 100th edition of the race.

Less than two weeks after the tragic death of former Astana teammate Michele Scarponi, there is a nascent expectation on Nibali to honour the 37-year-old's memory by conquering his third Giro title.

But despite triumphing twice (2013, 2016), either side of a maiden Tour de France triumph in 2015, Colombian Nairo Quintana -- not Nibali -- is the favourite for a particularly gruelling 100th edition of the race, first held in 1909.

As a result, 32-year-old Bahrain team leader Nibali will opt for a "cautious approach" and try to keep his powder dry for a "terrible" third week that includes several punishing climbs at high altitude.

"We've put in the work as a team to be here in the best condition possible. I have a lot of respect for my adversaries," Nibali said Wednesday, two days before the first of three stages in Sardinia takes the peloton over 206km from Alghero to Olbia.

"It'll be a long challenge with a lot of unknowns. (Event director) Mauro Vegni has made the route even more difficult than in previous years.

"It's not easy to be on the highest (podium) step so if it's not possible to win the Giro again, I'll fight for second or third place to honor the race.

"But I prefer to go cautiously, because the third week is terrible."

On a 3,609km-long route that has something for everyone, more than a few rivals will be looking to throw a spanner into the works, and Quintana is the man on everyone's lips.

"Nairo Quintana is the favorite," said Tom Dumoulin (Team Giant), one of two Dutch contenders along with Steven Kruijswijk (LottoNL).

"In the past years and last month, he's been showing that even at 90 percent of his capacities, he can win."

- Quintana eyeing double -

But Quintana, the 2014 Giro champion and defending Tour of Spain champion, isn't content just to go for victory in Italy.

He hopes it would spur him on to a rarely-achieved Giro-Tour de France double, saying last week: "We've never tried this before but we think we're on the right track, with a training programme adapted to arriving at both in form."

A two-time Tour de France runner-up, to Chris Froome in 2013 then Nibali in 2015, Quintana says he has enough Grand Tour experience to emulate now deceased Italian great Marco Pantani, the last rider to achieve the feat in 1998.

"I feel this year I've got a little bit more maturity and resistence in the body. That's why I think it's the time to do it, when you're in a good physical condition."

As well as Pantani, the race will pay homage to fellow Italian cycling greats Gino Bartali, Fausto Coppi and Felice Gimondi.

The first week climaxes with a 14-kilometre climb to Blockhaus, at 1,674 metres, on stage nine, while the first of two individual time trials comes after the second rest day, held over 39.2 km in the Sagrantino wine-growing region.

Stage 11's ride from Florence to Bagno di Romagna will pass through the birthplace of three-time champion Bartali and two days later, five-time winner Coppi will be honoured when stage 13 ends in Tortona, where he died in 1960.

After a rest day in Bergamo, the birthplace of three-time race winner Gimondi, the peloton will look ahead to the decisive final week with trepidation.

Despite only two summit finishes in five days of climbing, the pink jersey contenders are in for a punishing final week that includes climbing over legendary passes like the Mortirolo and Stelvio.

Before then, Pantani will be remembered on stage 14 from Castellania to Oropa, where he completed an astonishing climb to victory in 1999 before being thrown out the race for suspected doping a day before the finale.

The race ends in Milan on May 28, following the second time trial, from Monza racing track to Milan.

source: AFP