It's finally here. After the early skirmishes and the tactical manouvres, the first of the 2017 Tour de France's major high mountain showdowns has finally arrived.
Stage nine's criss-crossing trek through the southern half of the Jura,tots up to seven classified climbs, one second category, three of them Hors Categorie, culminating in the dauntingly difficult Mont du Chat and its perilous descent to Chambery. Some contenders see it as the most difficult single day of the entire Tour de France.
Others disagree, claiming the double-whammy of two stages in the Alps is even harder, but whoever's right, nobody would disagree that the 181 kilometres of stage nine of the Tour from Nantua to Chambery should open up a whole new chapter of the 2017 Tour de France.
As Movistar Team manager Eusebio Unzue observed after stage eight, following such a tough stage on Saturday through the northern Jura mountains, Sunday's sequel could create bigger differences than expected. And if it rains, as is forecast, then stage nine could throw up even greater challenges.
In fact, this Sunday, Unzue predicted to Spanish radio station Cadena Ser, will be absolutely key to the overall outcome of the Tour.
"It's a stage that's got 5,000 metres of vertical climbing and we'll surely see some very important consequences. Given the way the Tour has reached this particular point of the race, and after such a hard stage, I'm sure on Sunday we'll see a big part of how the race looks in Paris.
"There aren't going to be any hiding places. You have to be in good shape."
The knock-on effects of Saturday, Unzue told Cadena Ser, will make for an even tougher race Sunday.
"It's always the same," Unzue said "you may get through one stage like Saturday's, but then there are always big knock-on consequences.
"A lot of the earlier stages have been dominated by the sprinters teams, and so a lot of riders were still fresh for the mountains, which is why you got such a big break on Saturday and everybody wanting to be in it.
"So we had a stage like Saturday, raced in these Jura mountains and valley roads in temperatures so hot it feels like you're in an oven, and which went really fast from start to finish.
"I think tomorrow [Sunday] is the second big exam after today and we're really going to see a lot of what's going to happen in this year's Tour."
Unzue's words were echoed by race leader Chris Froome (Sky), who said in his post stage press conference on Saturday, that "Tomorrow will even more selective, we could really see the GC get blown to pieces. If it's raining on the descent, that could definitely play a big part in all of it."
Whilst Unzue says he is confident Movistar's contender for the Tour, Nairo Quintana is slowly but surely hitting top form - something the Colombian seemed to confirm on Saturday, although he was wary about whether he would attack or not - Unzue also said he had not expected Fabio Aru's strong attack on the Planche des Belles Filles last Wednesday, the one real omen so far for what could happen on Sunday's trek through the Jura.
"I was surprised at how well Aru (Astana Pro Cycling Team) was going there. Richie Porte (BMC Racing) was the man in form in the build-up to the Tour and if you look at the way BMC rode on the stage on Wednesday they were clearly going for the stage and the time bonus," he told Cadena Ser.
"Then what happened, happened, Aru was flying and the rest of the favourites were in a range of 14 seconds."
The counter-argument to all of these predictions of sparks flying in Sunday's Jura stage is that the favourites will be so daunted by the prospect of so much hard climbing that they will simply race conservatively. Rainy weather, particularly on such a dangerous descent to the finish may dampen even the most aggressive of spirits.
There's two weeks racing to go after the Jura, after all, and cycling's Grand Tour history is littered with ultra-hard stages that have backfired spectacularly and proved far duller than had been expected. Look no further than the Jura stage last year, won by Jarlinson Pantano, which - with no disrespect to the Colombian - lacked the fireworks between the GC contenders we'd be hoping would happen.
But the terrain is there, for sure, and the opportunities are there for some real GC fireworks. Keep your fingers crossed.