The key mountain stage of the Vuelta a España takes place on Saturday, with over 5,000 metres of vertical climbing, a summit finish on the much-feared Col d'Aubisque, and some potentially decisive developments in the battle for outright victory in Madrid on September 11th.
"It's a very important stage, this one is the queen stage of the Vuelta, and Nairo Quintana's [current GC] advantage of 54 seconds over Chris Froome (Team Sky) is maybe not sufficient, not with a time trial of 37 kilometres to come," ASO boss Christian Prudhomme tells Cyclingnews.
Prudhomme expects a major battle between the two: "Quintana (Movistar) maybe needs a minute or more on Froome. What we've seen so far is that Froome is marginally better than Quintana on the short, explosive climbs [stage 3 and stage 10] but on the long cols [stage 8 and stage 10] it's more Quintana who's had the upper hand."
"Now we've reached the Aubisque, and a stage almost entirely on French soil. In a Vuelta, which is 100 percent Spanish but which has ASO behind it too, is a really nice symbol of the co-operation between France and Spain through cycling and ASO."
"There have been two finishes in the Tour de France on the Aubisque" - 1985 with a win for Stephen Roche and in 2007 for Michael Rasmussen - "and it's going to be a hugely important stage for the Vuelta."
Prior to the Aubisque on the 196 kilometre stage are three category 1 climbs, the Col Inharpu at kilometre 62, the Col du Soudet [24 kilometres at km 118.2) and the Col de Marie-Blanque [km 157]. But it is the Col d'Aubisque [km 196: 16.5 kilometres at average of 7.1 percent.] which will almost certainly see the real showdown between the major favourites.
Former rider Roberto Laiseka, now with Unipublic, went over the Aubisque back in his first ever Vuelta in 1994, and says up until 12km into the Col d'Aubisque ascent, at the village of Gourette, the climb doesn't seem that hard. "But then in the last four kilometres it gets really difficult.
"The road isn't half as well tarmac'd, it's much more difficult and then the total length of that stage is going to be tough, too. It's surely going to be important."
Not everybody agrees. "I don't see much happening," Tinkoff sports director Sean Yates tell Cyclingnews. "In terms of climbing metres it's the hardest, but it all depends on how they do it."
"There are two teams, Movistar and Sky, who really want to control things in the race, and they know that Quintana needs to take more time."
"In my opinion, it's much easier to take time differences on the shorter, punchier climbs than it is on a stage like the Aubisque, which isn't that steep and won't really tax the guys like Froome and Quintana. They're used to these kinds of climbs, and they'll be dictating things, and they'll just follow each other.
"Movistar and Sky can each get five guys over each of these climbs, they control each other and control the race between them."
"Who's going to attack on the Marie-Blanque?" Yates asks rhetorically. "If Quintana did that, Froome will follow him. And the Aubisque has some quite steep pitches at the start, but it's mainly quite craggy."
Quintana, in any case, as Chrisitan Prudhomme says, is all but obliged to try to gain time on Froome, and the Aubisque, in the Colombian's eyes, may yet represent a key opportunity. However, after Peña Cabarga, it is possible that Froome has now ridden himself in to the Vuelta to the point where he may try to take the race to the Colombian instead.
Then there are still riders like Esteban Chaves (Orica-BikeExchange), Alberto Contador (Tinkoff) who may regard such a difficult stage as a last major opportunity to impact on the overall. Either way, the sparks may well fly.
Stage 13 highlights