CHAMPAGNEY, France — After losing two of its biggest stars in one horror crash, the Tour de France needed a pick-me-up.
Italy's Fabio Aru answered the call.
On the first mountain climb of this 104th Tour, after the lower altitudes where Mark Cavendish and Peter Sagan were forced out of the race — the first with a broken shoulder, the second disqualified — Aru showed Wednesday he could be the man to beat by leaving three-time champion Chris Froome in his wake.
Making up for the bitterness in May of missing his home grand tour, the Giro d'Italia, Aru zoomed away from Froome and other top riders yearning to ride into Paris in the yellow jersey on July 23. The punishing climb to the Planches des Belles Filles ski station in eastern France's Vosges mountains was made to look like a mere speed bump.
Froome played down Aru's show of strength in winning Stage 5, noting there are still 16 more days of racing to go. But 32-year-old veteran also acknowledged making a rookie's mistake by not reacting quickly enough when the 26-year-old Sardinian slammed on his pedals.
Along the steep crowd-lined hairpin bends through dense pines, Aru rose from his saddle and rocked powerfully from side to side as he gobbled up the mountain in his Italian national champion's jersey of green, white and red.
Froome got the message, loud and clear.
"This is going to be the hardest-fought battle I've had," he said. "We definitely cannot give Fabio that kind of space again."
Wednesday's 160.5-kilometer (100-mile) ride started in the spa town of Vittel which, like Froome, has seen better days — with shuttered hotels fallen into disrepair.
At the foot of the 5.9-kilometer (3.1-mile) finishing climb to an altitude of 1,035 meters (3,395 feet), everything seemed to be going to plan for Froome. His Sky teammates were powering up the ascent ahead of him, leading their champion up at a fierce pace aimed at dissuading other riders from attacking.
Aru hadn't read the script.
Despite the effort of his sudden acceleration with more than 2 kilometers (1 1/2 miles) left to climb, he was lucid enough when powering away to yell at a roadside spectator who got too close to him and to toss a water bottle at the feet of another. He still had energy to spare at the top to finish with a sprint.
When Froome finally reacted, upping his tempo, it was already too late: Aru was gone.
"When he left, I stayed with my team and waited for the attack from the others," Froome said. "But no one moved. I thought, 'OK, I have to go, what can I do?'"
"There's a flat before the last climb and perhaps we waited too long there."
A consolation: Froome took the race leader's yellow jersey off the shoulders of his teammate Geraint Thomas, who couldn't stay with the leaders on the climb made doubly punishing by searing summer temperatures.
Irish rider Dan Martin of the Quickstep team was second to the top, surprising Froome with his own burst of speed on a very steep section near the finish. Froome came in third, 20 seconds behind Aru — who had never climbed the ascent before but watched video of Froome winning the first time the Tour climbed it in 2012.
"It's extraordinary for me to win this stage," said Aru, a two-time podium finisher at the Tour of Italy and winner of the 2015 Tour of Spain. He was devastated not to have been there when this year's Giro started from his home island of Sardinia, having injured a knee in a training crash.
"I'm someone who prefers to maintain a low profile. It's not necessary to say that I'm extremely happy. A victory in the Tour is something fantastic after difficult months with my injury," he said.
"Only my family and the people close to me know what I went through," he said. "Having the Giro in Sardinia is not something that happens every year. Fortunately my home fans embraced me anyhow and I was able to focus on the Tour immediately."
"Getting back in the saddle gave me my smile back."
The last person to win at the Planches des Belles Filles, Vincenzo Nibali in 2014, also was Italian and went on to win the Tour that year. Although not as monstrous as those to come in the Pyrenees and Alps, the climb is tough enough to offer an early gauge of who the strongest riders are this year.
Two-time champion Alberto Contador doesn't seem to be among them. He placed eighth on the climb, 26 seconds slower than Aru and six seconds behind Froome. Three-time podium finisher Nairo Quintana also struggled, possibly paying the price for riding the Giro in May. The Colombian placed ninth, 34 seconds behind Aru and 14 behind Froome.
"We got a little preview of just where everyone's at in terms of their condition," said Froome. But the Briton advised against jumping too quickly to conclusions on the basis of this first climb.
"It's still very open, we've got a lot of racing ahead of us."
Overall, Froome leads Thomas by 12 seconds. Aru jumped from 25th to third in the standings, and is 14 seconds behind Froome. Stage 6 on Thursday cuts through Champagne country from Vesoul to Troyes and is flat enough for sprinters encouraged by the departure of Cavendish and Sagan to go for the win.