Chris Froome is not as strong in this 2017 Tour de France as he was in 2016, according to leading figures within Astana.

The Team Sky rider could not stay with his rivals on the steep grades to the Peyragudes summit finish on stage 12. He lost 22 seconds to the stage winner and slipped out of the yellow jersey, six seconds back on new leader Fabio Aru (Astana).

>>> Chris Froome loses yellow jersey to Fabio Aru as Romain Bardet wins Tour de France summit finish

“Sky did a great job to try to win the stage today,” Astana general manager Alexandre Vinokourov told Cycling Weekly next to the airstrip finish.

“You see that Mikel Landa is very strong, too. Froome should’ve won the stage for his Tour win, but you saw that he’s not as strong as last year. No he’s not, not for me. Because of this, we have more motivation for the next stages.”

>>> Fabio Aru: ‘I saw Chris out the back… and realised I had the yellow jersey’

Astana won the Tour de France with Vincenzo Nibali in 2014 after Froome abandoned due to crashes. Froome returned in 2015 and 2016 to win his second and third titles.

Some have questioned Froome’s strength leading into the Tour de France given he has yet to win a stage in 2017. In previous seasons, he showed greater domination heading into the Tour.

Watch: Tour de France stage 12 highlights

Sardinian Aru may have the leader’s jersey, but his team is much weaker than Sky. Helper Dario Cataldo abandoned after a crash in stage 11 and star captain Jakob Fuglsang continues with a fractured wrist and elbow.

“I hope he continues for the next stages because we really need him for the next mountain stages. We will talk to the doctor, but we face a difficult stage [today]. I hope Jakob recovers,” Vinokourov added.

“Why can’t Aru win the Tour? We are here to win, but Froome is always strong, and there’s also Romain Bardet and Rigoberto Uran.”

Froome moved into the yellow jersey on stage five after Sky’s Geraint Thomas held it for the opening four days.

>>> Chris Froome: ‘No excuses’ for losing Tour de France lead on stage 12 summit finish

“We thought that Froome was going for the stage given how he was having his team work, maybe he just lacked the legs in the final, but you can’t take anything away from him as a rider,” Astana team manager Giuseppe Martinelli said.

“[The final kick was] more adapted for the climbers than Froome, who paid more than the others, but for me, Froome remains the number one. Froome and Bardet are the strongest, we have to take advantage of them.

“But we need to keep our feet our on the ground. We lost a rider and a half, Jakob is bad off. We have Bardet who’s strong, and Froome’s still strong.”

Aru already counts a Vuelta a España win from 2015. Also in 2015, he finished second to Alberto Contador in the Giro d’Italia.