Froome leads Colombian Rigoberto Urán (Cannondale-Drapac) and Frenchman Romain Bardet (Ag2r La Mondiale) by 27 seconds in the overall classification with four days to race. On Thursday, they finish on the Col d’Izoard, the race’s final summit finish.
“If someone is strong tomorrow, he has to go,” Astana sports director Dimitri Fofonov told Cycling Weekly.
“We are there in the running with Fabio and we will see what will happen, I hope Fabio is there to do so, but at this point it’s Bardet’s race to win. He is ready to take on the big fight.”
The 26-year-old placed second overall behind Froome in the 2016 Tour.
Bardet attacked Froome’s yellow jersey at least three times on the famous Col du Galibier during stage 17. Froome responded always with Urán. Sky team-mate Mikel Landa, fifth overall, lost pace but returned and worked for his leader.
Sardinian Fabio Aru lost contact near the top. He trailed around 10 seconds back and lost more on the descent, coming over the finish line 31 seconds back.
“For sure, I can’t be content,” Aru said while warming down in his Italian championship jersey.
“But the Tour finishes on Sunday. For sure, not a great day for me, but this is cycling and you have to accept these days when you lose.
“We were at a certain altitude. When [Dan Martin] attacked, I didn’t have the energy to respond, and that was it.”
Bardet followed Dan Martin’s (Quick-Step) move with several digs. He appeared most alive and most likely to ride clear on the Col d’Izoard summit finish on stage 18.
“Bardet was strong today, he made all the selection today. Froome wasn’t great today, he wasn’t in trouble, but he had trouble to take him,” Fofonov added.
“Landa returned to make the pace. Also Urán, we never talk about him, but he’s always there and he’s responding to attacks when he need too.”
After the Izoard stage, the Tour continues with medium mountain stage, a time trial in Marseille in Froome’s favour and a flat stage to Paris on Sunday.