Vincenzo Nibali is in the driver's seat as the...

Does Nibali risk running out of fuel before Tour pulls into Paris?

Astana trainer, Paolo Slongo, keeps a close eye on Nibali's numbers as the race heads through the Pyrénées and on to Paris

CARCASSONNE, France (VN) — Vincenzo Nibali (Astana) is in charge of the Tour de France as it enjoys its second day off, but he could be at risk of running out of fuel before the race ends Sunday in Paris.

In the Tour, 4:37 over nearest rival Alejandro Valverde (Movistar) may appear to be a lot, but as Richie Porte (Sky) realized Friday, the GC can crumble in a flash. For this reason, Astana’s trainer, Paolo Slongo, keeps a close eye on Nibali’s numbers as the race prepares for its final stages through the Pyrénées and on to Paris.

Slongo unclips the yellow SRM computer, cycling’s equivalent to a flight data recorder, from Nibali’s handlebars after every stage to analyze his power output. Too much energy spent in one stage could mean his star rider won’t have enough for the next important day.

“I’ve seen it happen before to others, but for unknown reasons, maybe messed up their diet or they are sick,” Slongo told VeloNews. “Chris Froome on Alpe d’Huez last year looked to be in trouble at one point, but lucky he only slipped back when it was five to six kilometers to go, because if that happens on the penultimate climb, 50 kilometers from the finish …

“In Nibali’s case, that four or so minutes wouldn’t be enough. You can lose six to 10 minutes like that.”

Porte lost 8:48 and slipped from what seemed like a firm second spot in the GC to 16th place Friday when the race climbed to Chamrousse. Michal Kwiatkowski (Omega Pharma-Quick Step) dropped from 11th to 16th the next day, on a vicious alpine stage to Risoul.

Nibali is going well, so well that he even catches Slongo by surprise. Saturday, the idea was that he would attack closer to the line, instead he went solo 6.6 kilometers out. He gained time, but used a lot of energy doing so.

“He was behind Valverde and Pinot, and technically he’s saving 20 watts doing so. He can understand himself better, though. It’s another thing sitting in the team car, you need to make the call yourself,” Slongo said.

“Our concern is that he remains protected, like he has been, and that he takes advantage of all the situations. He shouldn’t give help to Valverde, Pinot, Bardet … He has to take advantage of everything.”

Some critics look to last year’s Vuelta a España and raise an eyebrow. Nibali looked like he had a second title secured but lost it in the closing days to Chris Horner, who became the oldest grand tour winner in history at 41 — 13 years older than Nibali.

Slongo explained that after Nibali won the 2013 Giro d’Italia in May, he had two weeks off and had to go to Kazakhstan to meet sponsors. In total, he spent nearly a month off the bike, suffered when he returned in the Tour of Poland, and had no base for the Vuelta.

With a slow build up since the Tour de Romandie in May, Slongo said that the 2014 Tour its different.

“He was within his limits in the Alps, so he should be able to maintain this to Paris,” continued Slongo.

“The risk? Maybe he’ll have a crisis, an off day, like Porte. If it is a flat day, then you’re lucky, but if you’re in the mountains then you have to fake it and hope that you’re rivals don’t figure you out.”