George Russell has described Alex Albon's decision to return for the Singapore Grand Prix as "audacious", praising the Williams driver's determination to feature in what he feels is Formula One's "toughest race".
Albon spent a night in intensive care earlier in September after suffering respiratory failure following treatment for appendicitis.
The 26-year-old was then replaced by Nyck de Vries for the Italian Grand Prix, but is set to return to the grid this weekend.
The Singapore race is the longest of the F1 season, while the humid conditions at the Marina Bay Street Circuit are expected to test drivers' stamina.
Russell – whose move to Mercedes paved the way for Albon to assume his seat with Williams – has been impressed by his recovery, saying: "It's definitely audacious to come back for the toughest race of the season having only just recovered.
"But it just goes to show the sort of grit and determination he has. I was in contact with his family on the Saturday night because it was looking very scary at one point.
"But it's pretty impressive to see how he recovered so quickly. The human body is a scary thing.
"It just goes to show one minute everything is fine, and the next minute everything can change almost totally out of your control. It will be interesting to see how he gets on this weekend."
Asked about the difficult conditions drivers will face this weekend, Russell added: "It doesn't matter how much training you do, you will never be able to replicate what you go through on track.
"I have been training with at least three layers of clothes on every single gym session, every time I go out on the bike.
"It's pretty uncomfortable. It's quite impressive how difficult the body handles heat, even in the sauna for half an hour. That's what we will be experiencing in the car. And then there is the physical element and cognitive side of things."