The Team Sky rider leads team mate Geraint Thomas by 12 seconds with Fabio Aru (Astana), who made quite an impression when he prevailed in the first summit finish on Wednesday, in third place 14 seconds off the pace.
But the first big rendezvous between the top guns is expected on Sunday, when the peloton goes up the Col de la Biche (10.5km at an average gradient of 9 per cent), the Col du Grand Colombier (8.5km at 9.9 per cent) and the Mont du Chat (8.7km at 10.3 per cent) before a dangerous descent into Chambery.
"It is going be an important block these next two days but Sunday's stage will be very decisive with a lot of climbing and we will see a lot of damage," said Froome, who won the Tour in 2013, 2015 and 2016.
Froome and all of his rivals, with the notable exception of Nairo Quintana (Movistar), got a feel of the stage during last month's Critérium du Dauphiné when the race went up and down the Mont du Chat.
"If anything it was more of getting a feel of the climb to the Mont du Chat and the descent," said Froome.
"I'm certainly grateful that I have seen the climb. I know what I'm up against. But it is going to be much tougher than on the Dauphiné because of the climbs that come before."
On Wednesday Froome possibly underestimated Aru as he let the Astana rider pedal away up La Planche des Belles Filles, but he now considers himself as having been warned.
"He's very close in the GC (general classification), I will need to pay attention to him. (Last year's runner-up Romain) Bardet (AG2R) knows the Mont du Chat descent very well, too," he said.
while Bardet knows the area as his team is based near Chambery, Froome is confident his team can control the stage.
"Thankfully we haven't had to do a lot of riding in the front because the sprinters' teams controlled several stages and BMC took it on in the only mountain stage," he said, referring to Australian Richie Porte's team.
"Relatively speaking the (Team Sky) guys are still fresh, that's a blessing for us."
Aru will not be the only man to watch, though.
"Certainly Fabio Aru is threatening and looking at the GC he is my closest rival but at this point, I would not say he is any more of a threat than Richie," Froome said.
"It's still very close in the top 10 but this weekend we will see where everyone is at."