Chris Froome (Team Sky) will start the final mountain stage of this year's race in prime position to add to his three-previous wins. Froome's rivals must take on the race if they want to wear yellow into Paris knowing Froome is likely to claw back time in the stage 20 time trial.
The mythic Col d'Izoard first appeared in the Tour back in 1922 and has since been utilised by race organisers on a further 33 occasions. However, 2017 will be a special occasion in the history of the Tour as the Casse Déserte hosts a stage finish for the first time with race organsiers hoping it blows apart the GC battle.
Colombian Rigoberto Uran (Cannondale-Drapac) and Romain Bardet (AG2R-La Mondiale) are tied in second place at 27 seconds to Froome with former yellow jersey holder Fabio Aru (Astana) fourth at 53 seconds. Mikel Landa in fifth place at 1:24 minutes to Froome would in another context be regarded as a dark horse for the win except for the fact he is Froome's key domestique.
Adding to the intrigue ahead of the Col d'Izoard showdown, of the top-five, only Bardet was present Tour when it visited the Alpine climb in 2014.
Throughout the 2017 Tour, Bardet and Dan Martin (Quick-Step Floors) have consistently been the riders most likely to take up the fight against Froome and Sky. Both riders rolled the ride on stage 17 to Serre Chevalier but ended the day conceding time to Froome.
Despite their time losses, expect more of the same from the duo who could concede over one minute to Froome in the stage 20 Marseille time trial.
"I've been faithful to my philosophy since the start of the Tour, attacking and trying to make things happen," a defiant Bardet said post-stage.
"Disco Dan's back again, I guess. I can dance again, just in time for Paris," sixth placed Martin added.
While Uran is yet to light up the climbs with attacks of his own, the Cannondale-Drapac rider has ridden a canny and intelligent race with his stage 9 victory arguably a career highlight. A strong rouleur, Uran won't need to be as aggressive as Bardet and Aru, who said after stage 17 that "my Tour doesn't end here," on the Izoard. However, he would benefit by forming an alliance with Bardet and Aru to take on Froome, as his former teammate sees the Colombian as his major rival.Thursday is also the Colombian day of independence, further motivated should Uran need it.
"If the gaps remain like this, then Rigoberto would be the biggest rival of those guys," said Froome.
At this year's Tour, Froome has extended his stay in the yellow jersey over the 50-day mark, now fourth of all time, but the Briton is yet to show his impervious form of his 2013, 2015 and 2016 Tour winning years. Froome hasn't won a race since stage 19 of last year's Vuelta a España and a win atop the Izoard, in the yellow jersey no less, would all but seal a fourth career win. And with Aru, Bardet, and Uran all claiming stage wins thus far, it would be a strange sight to see Froome arrive in Paris in yellow without a stage to his name. And the 32-year-old isn't keen on joining Firmin Lambot, Roger Walkowiak, Gastone Nencini, Lucien Aimar, Greg LeMond, and Óscar Pereiro in claiming yellow without a stage win.
"It is the equivalent of the Mont Ventoux on this year's Tour de France," Froome said, later adding: "It depends on where everyone's at and who has the legs tomorrow. If I have an opportunity, I'll go for it."
The first six times the Col d'Izoard feature in the Tour, the peloton rolled out of Nice and finished in Briançon. Since the 1910 debut of the Col d'Izoard, Briançon has been the favoured finish location when the Izoard has been included in La Grand Boucle. For the first time since 1947, Briançon plays host on what will be the sixth time stage 18 of the Tour features the Izoard.
At 179.4km, stage 18 is the second shortest of the summit finishes in 2017 but far and away the highest in elevation. Rolling out of Briançon, it's the familair N94 that takes the peloton south through to Embrun. Whereas the peloton follows the N94 over the Lac de Serre-Ponçon after stage 19's start in Embrun, stage 18 takes the peloton over the stunning Côte des Demoiselles Coiffées. An upstream gradual climb alongside the banks of the River Urbaye is likely to see attacks before the peloton takes the left turn at Saint-Paul-sur-Urbaye for the long awaited return to the Col du Vars.
A 9.3 kilometre-long climb at 7.5%, the Col du Vars' hits sections of 10% from Le Mélèzen for two kilometres before ever so slightly evening out towards the top. A fast descent into Guillestre is likely to follow with riders pushing the pace before the D902 valley road into the base of the Col d'Izoard
The 14km climb up the Col d'Izoard is where the race will come to life with a possible breakaway battle for the stage and Sky controlling Froome's rivals with an impossibly high pace to deter attacks.
There is no respite on the Col d'Izoard as the riders head towards its 2,360-metre summit. An opening half between 5-7 % gives way to the average 9% percent, bar the brief respite at Col de la Platrière before the road kicks up in the final kilometre.
Although there are thunderstorms predicted for Friday at Izoard, the Thursday weather prediction is somewhat milder with clouds, 30% possibility of rain during the stage and strong gusts. Compared to last year's denouement in the Alps when Bardet took the stage win and surged to second overall as Aru faded and dropped out the top-ten, it is unlikely the weather will be a major player on the Izoard. But then again, this Tour has delivered the unpredictable.
The other-worldly setting of the Casse Déserte has witnessed some of the Tour's greatest moments, Fausto Coppi, Louison Bobet, Eddy Merckx and Bernard Thévanet, Bernard Hinault and Greg LeMond, and Andy Schleck in 2011. The Tour's third visit of the 2010s is positioned to deliver another classic finale with the added intrigue of the Tour's closest general classification battle this deep into a race. By the end of the Col d'Izoard, the GC battle could be blown to pieces with the yellow jersey dreams of at least one rider shattered for another year.
With double king of the mountains points on the line for the winner, throw into the mix the battle for the polka dots, and it's hard to argue against the balanced route crafted by Theirry Gouvenou to ensure the race for yellow it so tightly poised this late into the Tour.