Tour de France 2014: Vincenzo Nibali stamps his authority on the yellow jersey as he powers away from Richie Porte to stretch lead with stage 13 victory

Nibali faced his most testing climb so far but flourished as he pulled away from the rest of the field to win his third stage of this year's Tour

The Tour de France leader Vincenzo Nibali delivered a near-knockout blow in Friday’s first alpine summit finish, taking his third stage win and adding nearly a minute to his overall advantage. Meanwhile, Sky’s Richie Porte, who had been lying second behind the Italian, cracked badly.

The contrast between the way the 29-year-old Sicilian and the Australian, also 29, approached the finish line at the top of the 18-kilometre ascent to Chamrousse ski station could not have been more expressive of the duo’s different fortunes on a day of intense heat.

Alone and certain of his triumph, Nibali was still collected enough to zip up his yellow jersey of race leader as he rode towards the 33rd victory of his nine-year career. Then his usual inexpressive mask melted slightly into a faint grin, as it began to sink in that the chances of his winning Italy’s first Tour since 1998 had increased enormously.

Porte on the other hand had his Sky jersey wide open and was sweating heavily as he approached the line nearly nine minutes later. Fortunately the Tasmanian, who after Chris Froome’s abandonment was Sky’s “plan B” in the Tour, had team-mates Mikel Nieve and Geraint Thomas on hand to help shepherd him up the alpine col and limit the already considerable damage.

“It seemed like the final climb would never end,” Nibali, who now leads closest rival Spain’s Alejandro Valverde by the very comfortable margin of 3 minutes and 37 seconds, said afterwards. “I really suffered in the heat, but the higher we got, the better it got. I wanted to open up as much of a gap as possible when I saw Porte had cracked, and then I got the opportunity to go for the win, too.”

It did not seem to matter that as the peloton shredded on the final ascent to Chamrousse, Nibali only had one Astana team-mate, Tanel Kangert, as support.

Valverde’s Movistar squad initially kept the pace high, which effectively did Nibali’s job for him, and then shortly after that Porte cracked – around a third of the way up the climb – when the Spanish veteran opted for an all-out attack to which only Nibali and France’s Thibaut Pinot were able to respond.

As Porte drifted further and further behind, losing 30 seconds in less than half a kilometre, Nibali then launched his first telling blow, blasting up the right-hand side of the road with a long surge. In no time at all the Italian’s workmanlike but resoundingly steady style of pedalling brought him quickly up to two earlier breakaways, Pole Rafal Majka and Czech Leopold König,  while Valverde and Pinot’s limited co-operation behind  helped the gap widen yet further.

And then, some three kilometres from the line, having cleverly all but obliged the two breakaways to keep a high pace – with two stage wins in the bag already, at Sheffield and Les Planche des Belles Filles, Nibali had less to lose – he made another of his almost imperceptible but ruthlessly effective accelerations.

Once again Nibali’s surge ahead had the effect of leaving his two final opponents reeling, and a few minutes later, as he crossed the line for his third triumph in 12 days, it brought a Tour victory much closer than 24 hours before. “Getting that win,” Nibali said, “felt like a liberation.”

Third in the 2012 Tour de France and already the winner of two of cycling’s Grand Tours, the Vuelta a Espana and the Giro d’Italia, Nibali – who also moved into the lead of the King of the Mountains competition – recognised that “it wasn’t a very good start to the season, but since the summer started I’ve managed to turn things around pretty well.”

Nibali’s victory on Friday came on a significant date for Italian cycling, too: the 100th anniversary of the birth of one of the country’s greatest-ever riders, double Tour winner Gino Bartali and, as Nibali himself pointed out, the anniversary of the death of Fabio Casartelli in a crash in the Pyrenees in the 1995 Tour. “That’s very important to me, I remember that tragedy,” he said.

While Friday’s victory confirms that Nibali is the rider to beat, Porte’s below-expectations performance means that following two overall wins in 2012 and 2013, Sky will now be all but obliged to revert to their 2010 and 2011 Tour strategies and almost certainly will be fighting for stage wins at most.

“I don’t think I dealt with the heat very well,” Porte, now 16th overall,  admitted on his team’s website. “It’s one of those things. It’s a massive shame but we’ll see what happens tomorrow.

“We’re not just going to roll over”, Team Sky principal  Sir Dave Brailsford added. “Obviously it was a blow losing Chris when we were coming here to try to win the race, and certainly seeing how Nibali’s going, it would have been an interesting race, that’s for sure. And then recalibrating to our plan B, as it were,  and now we’ve got to recalibrate again.”