CHAMPAGNEY, France — Two Tour de France rookies stole the show on the first mountain stage, with Dylan Teuns of Belgium winning Stage 6 and Giulio Ciccone of Italy taking the overall lead on Thursday.
Geraint Thomas, the defending champion, also rode strongly, going some way to answer questions about his fitness after he crashed out of the Tour de Suisse in June. Thomas rode in fourth at the top of the difficult climb to the Planche des Belles Filles ski station in the woody Vosges Mountains of eastern France.
But the severity of the ascent — with a final 24 percent incline and an unpaved section that kicked up clouds of dust — torpedoed other main contenders for the overall victory in Paris on July 28. Some riders were so exhausted at the top that race workers had to help them stay upright on their bikes after they crossed the line.
One of the big losers of the day was the French rider Romain Bardet, a podium finisher in 2016 and 2017, who cracked and rode in 1 minute 9 seconds after Thomas. He suffered the added indignity of his chain’s jumping on the line, immobilizing him. Now 2:08 behind Thomas over all, Bardet will be hard-pressed to make up that deficit on even harder climbs to come in the Alps and Pyrenees.
Vincenzo Nibali, the 2014 Tour champion from Italy who also won the stage to La Planche des Belles Filles that year, came undone this time. He lost 51 seconds to Thomas on the climb and is well down the overall rankings in 20th place, 1:07 behind Thomas.
Teuns and Ciccone, both racing their first Tour, were rewarded for their enterprise and endurance on the climb and for having been part of a breakaway of 14 riders that sped away from the pack early in the 100-mile trek from Mulhouse that took the Tour up six climbs before hitting the final and hardest one.
At the top of that final ascent, Teuns and Ciccone were the two survivors of their group, fighting head to head for the win.
Ciccone cracked first on the eye-poppingly steep incline as Teuns cranked on ahead of him to the line.
“It was really hard,” Teuns said. “A man-to-man fight. I finished it off. It was amazing.”
But Ciccone got a delightful consolation prize, in the shape of the yellow jersey.
“It’s an incredible day,” he said. “I can’t grasp what’s happening.”
Having raced in the Giro d’Italia in May, where he won a stage, Ciccone, 24, came to the Tour to bank some experience. The yellow jersey was never in his plans.
“It’s strange but super good,” he said.
The last three riders to hold the yellow jersey at the top of the Planche des Belles Filles all went on to win in Paris: Bradley Wiggins in 2012, Nibali in 2014 and Chris Froome in 2017.
But Ciccone does not expect to follow in their footsteps. His Trek-Segafredo team is built around the Australian rider Richie Porte, who was also dropped by Thomas but limited the damage, riding in just nine seconds after him.
Thomas, who finished ahead of Egan Bernal, his teammate at Ineos, climbed to fifth over all, 49 seconds behind Ciccone. He leapfrogged Bernal, who was in sixth and four seconds behind Thomas.
“It was a decent day,” Thomas said.
The previous wearer of the yellow jersey, the French rider Julian Alaphilippe, did everything he could to keep it, battling up the ascent through the dust.
But Alaphilippe fell just six seconds short, losing the race lead he first took on Stage 3.