Froome leads the Tour with 23 seconds on Romain Bardet (Ag2r La Mondiale) and 29 seconds on Rigoberto Urán (Cannondale-Drapac) after stage 18's Col d'Izoard summit finish.
The only real test remains the 22.5-kilometre time trial in Marseille on Saturday.
"You can't pull off miracles, especially when you have these rivals," Astana team manager Giuseppe Martinelli told Cycling Weekly.
"I've been saying since the first day that he's the strongest rider, so it's going to be [Froome victory]."
A victory would mark number four for the 32-year-old Kenyan-born Brit. However, this is his narrowest advantage yet coming into the final days.
Daniel Martin (Quick-Step Floors), who sits sixth overall, said: "I'd expect Chris to at least take one minute out of those guys in the time trial, no disrespect to those other guys, but he did nearly that in Düsseldorf. He'll be confident against those guys"
"I think he has enough time, he's the best in the time trial," said Sky team-mate Mikel Landa, who sits fourth overall. "It's not so much time, we'd be happier with more, but he's the favourite to win this Tour."
Sky sports director Nicolas Portal arrived in the white team car at the bus midway down the back side of the Izoard.
He had to use the bathroom after a long day in the car, but quickly and confidently remarked on the Marseille time trial and chances of a Paris party.
"Obviously it's not won, but it's better to be in yellow before the time trial," Portal explained.
"There's no room for a mistake or any bad luck. Clearly it's not over, but the hard stages in the mountains are now done. In theory he's a better time trial rider in than the others, but it's a tiny gap."
The favourites do sometimes fail to prevail in the final time trial.
Australian Cadel Evans looked ready to win the 2008 Tour given he was the best time triallist of the contenders, but he could not close the 1-34-minute gap to yellow jersey Carlos Sastre over 53 kilometres.
“And Urán is not a bad time triallist,” Serge Pauwels (Dimension Data) said.
“Remember when Sastre was in yellow in 2008, everyone thought Cadel Evans would win the Tour de France. It's looking good for Chris, but the pressure is on him."
"With this distance, anything can happen in a time trial," Trek-Segafredo sports director, Steven De Jongh said.
"I wouldn't be at ease behind him in the team car. He had two mechanicals earlier in this Tour. When you go at the limit in the time trial, there's always a risk, but the same as the other guys.
"But I hope a mechanical won't make the difference in this Tour."
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