Peyragudes - Chris Froome lost the yellow jersey for only the second time in four year's of Tour de France domination on Thursday, and the new holder's manager believes the Briton is now beatable.
Froome looked imperious in his three Tour victories in 2013, 2015 and last year, never giving his rivals a chance.
Only once before had he given up the yellow jersey, and that for just three days in 2015 to German Tony Martin, who wasn't an overall threat anyway.
This was the first time Froome had given up the jersey to a direct rival on a decisive stage, meaning Italian Fabio Aru is the new leader of the race, if only by six seconds.
"This shows that Froome is beatable," exhorted Alexander Vinokourov, Aru's Astana team manager.
On the final steep climb to the finish of Thursday's 214.5km stage from Pau to Peyragudes, Froome couldn't match the attack of stage winner Romain Bardet, nor that of Aru who finished third.
But the Italian is not getting carried away.
"It was such a hard last climb but I'd already done similar ones in the Vuelta (a Espana) so I was prepared," sad Aru.
"There's still a long way to go in the Tour, tomorrow (Friday) is another important stage. It will be quite dangerous and difficult."
Froome was gracious in defeat and didn't seem particularly concerned at having lost the yellow jersey.
"The race is certainly on now," he said with a smile.
His Sky sports director Nicolas Portal admitted they were unhappy to lose the jersey but there was no sense of panic stations.
"Let's just say it's never nice to lose the yellow jersey -- we lost it by just six seconds.
"It's not a disaster but it still hurts."
Not only did Aru strip Froome of the yellow jersey but the top of the standings closed up with Frenchman Bardet now third at just 25sec.
He too was reluctant to start banging nails into Froome's coffin, though.
"I don't know if he showed any weakness, it was a tough day and there will be more," said Bardet.
"It was a great day, the jersey changed hands and we can expect more changes to come."
Vinokourov, though, said this stage was significant, not least because Froome has often excelled in the Pyrenees in the past.
"If you look at the other Tours (Froome won), he always won the first stage in the Pyrenees," said the Kazakh, a former winner of the Vuelta when a rider, although he later served a doping suspension.
"Today I think Sky worked hard to try to win (the stage) but we saw that Froome is not as strong as in the other years, given that he didn't win today."
Froome was gracious in defeat, congratulating both Bardet and Aru, but he showed the steely determination that has helped him to win three Tours already.
"I had a bad moment there at the end. No excuses, I just didn't have the legs there in the final kick," he said.
"It's certainly going to be a big fight now all the way to Paris."
Colombian Rigoberto Uran was second to Bardet and originally saw himself move to within 35sec of Aru in fourth overall, until a 20-second penalty for illegally taking a water bottle in the final 10km sent him back to 55sec adrift of yellow, where he had started the day.
But he was satisfied.
"I'm really happy with how the Tour is going," he said.
"I was really close to winning the stage."
Everyone, though, is remaining wary of Friday's 100km Pyrenean stage.
It's an unusually short stage for a Grand Tour but it should be fast and fireworks are expected.
"The organisers want to make it a crazy race," said Bardet about Friday's stage.
"I hope to recover well for tomorrow, I'm really expecting a great battle -- even tougher than today.
"Sky are proud and will want to make up for today."