After Tuesday's 222km marathon queen stage over the Stelvio and the 219km transfer stage east on Wednesday, Tom Dumoulin's grip on the maglia rosa will be tested in a much shorter but far more intense stage in the Dolomites on Thursday.
The 137km stage is one of the shortest in the 100th Giro d'Italia but with nearly 4000 metres of climbing and five major passes in just four of hours of racing, it will again force Dumoulin and his Team Sunweb squad on the defensive.
With Nairo Quintana (Movistar) just 31 seconds back after the stage over the Stelvio, and Vincenzo Nibali (Bahrain-Merida) at only 1:12, the Colombian and the Sicilian believe they have a real chance of victory. Even after 17 stages the Giro d'Italia is on a knife-edge.
Because of the intensity and the density of the climbs over such a short distance, stage 18 has to be considered difficilissima," Race director Mauro Vegni said in the special Giro d'Italia created by Italian magazine Bicisport.
"It's hard to choose between the Stelvio stage and this stage as the real queen stage. Climbing the Stelvio twice is special but there is simply nowhere for the riders to catch their breath on stage 18."
Five climbs in 137km
The stage profile will be frightening to look as the teams and rider plan their strategy and prepare mentally for a third consecutive day of climbing.
A few may be dreaming of a special stage victory but most of the 166 riders left in the peloton will simply be hoping to finish within the extremely short time cut. Most will be racing to save their skin so they can move one day closer to finishing in Milan.
The stage starts in Moena at 1pm local time and climbs up the valley road to Canazei that hosted Pierre Rolland's emotional solo victory. This time the ski resort will be the start rather the finish of the day's climbing.
The Passo Pordoi is the first tooth of the day that has to be conquered. It is 11.9km long at 6.7% - a steady haul to an altitude of 2239 metres. It is followed by a fast descent to Cernadoi for the Passo Valparola – 12.3km at 6.4% and an altitude of 2200m. The riders will descend into the heart of the Alta Badia area and Corvara and climb through the stunning rock faces of the Dolomites via the Passo Gardena – 9.3km at 6.4% and an altitude of 2021m. None of the big three climbs are especially steep but all go over a stomach churning 2000 metres, which could test Dumoulin's resolve.
The Passo Gardena – 9.3km at 6.4% and an altitude of 2021m
Cruelly the stage route passes through Ortisei after 103km but descends all the way down to Ponte Gardena at just 467m before looping around and climbing back up the valley to 1219m via the little known Pontives climb – 9.3km at 6.8%, with a 9.3% final three kilometres.
The gradient eases just four kilometres from the finish, with a final kick up at 13% in Ortisei offering a launch pad for the perhaps vitally important time bonuses of 10-6-4 second to the first three finishers.
Ortisei has hosted a stage finish of the Giro d'Italia just twice before: in 1940, when Gino Bartali won ahead of his then young teammate in the pink jersey and future rival Fausto Coppi, and in 2005 when Colombia's Ivan Parra won the stage and Paolo Savoldelli pulled on the pink jersey on the way to wining his second Giro d'Italia.
Tom Dumoulin made it through Wednesday's stage with relative ease, finishing in the peloton, 7:54 down on Rolland and surrounded by his Team Sunweb teammates. His stomach problems of the Stelvio seem over for now and he munched on a salmon and rocket baguette before speaking to the media at the podium area.
"I'm not here to write history because I'm shitting in the bushes. I want to write history by getting the pink jersey in Milan," he said bluntly later to the written press, underlining his determination to fight for victory despite losing more than two minutes on Tuesday.
However the three climbs to over 2000 metres in the first 85km must surely be worrying him and his Sunweb team.
The Dutchman confirmed that he has suffered from the altitude/liquid food problem twice before. He was hampered by the problem in the Pyrenees at the 2016 Tour de France but it did not stop him winning the following day's stage to Andorra that finished at altitude of 2240m.
Reports in the Netherlands have suggested that high altitude forces blood from Dumoulin's stomach to his legs, sparking digestive problems after eating a number of gels rather than real food on long climbs.
Dumoulin has trained specifically for stages with multiple climbs and spent two special training at altitude this spring but does not seem to know why the problem occurs but will carefully plan what he eats on the climbs.
Dumoulin is confident he is strong enough to hold the pace set by an aggressive Movistar team on the 65.% gradual climbs on stage 18 but he also knows that he could quickly become isolated if Movistar set a super high pace on the first climb.
"We have to be ready for everything. Maybe the top 3 or top 5 will not attack on first climb – even if we have to be ready for that too – but definitely guys a little further away will try to jump away. That will happen, so it will be a big fight from the first climb," Dumoulin warned.
Team Sunweb lost Phil Bauhaus on Wednesday after the 22-year-old German struggled to recover from the intense racing of the Giro d'Italia. That leaves Dumoulin with just six teammates after Wilco Kelderman was hurt in the Blockhaus motorbike incident.
Despite their comparative weakness, especially compared to Movistar, the Team Sunweb riders are motivated and up for a fight.
"The problems of yesterday are behind us and were ready to fight," the USA's Chad Haga said, believing that Dumoulin can pull back as much as 1:30 in the final time trial to Milan even if he loses the pink jersey in the remaining three mountain stages.
"We've got a few crazy stages left and then we'll see how things stand. We expect full gas from start to finish on Thursday. On the short stages there's no holding back."
"Hopefully we've got enough gas in the tank. We've been using our matches wisely so far and we hope that pays off in the final, decisive mountain stages. It's awesome riding for the maglia rosa. We got to do it last year and it was special but this year we're in it to win it."
Everyone at Team Sunweb was amazed at Dumoulin's ability to fight back and limit his losses over the final Umbrailpass climb on Wednesday. He was timed as the fifth fastest rider on the climb and some how did enough to keep hold of the pink jersey despite his toilet stop and chasing alone for 33km.
"He was disappointed to lose time on a good day but if you look at it the other way around, they were only able to gain time on him when he stops to shit," teammate Simon Geschke pointed out, promising to give his all so that Dumoulin can again pull on the pink jersey in Ortisei.
Another successful stage would give Dumoulin a 15th day in the Maglia Rosa, more than both Savoldelli and Marco Pantani ever achieved. It would also be another huge step forward towards overall victory in Milan on Sunday.