Sainz took a remarkable victory for Ferrari on Sunday, just two weeks after undergoing surgery for appendicitis on the weekend of the Saudi Arabian Grand Prix, which he sat out.
That left the Spaniard with just a week to recover in time for the long trip to Australia.
While Sainz battled to be fighting fit for the Albert Park weekend, he feared that his Australia trip "wasn't going to happen" until the last moment.
"Nine days ago, when I was about to catch the flight to come to Australia, I was still in bed," Sainz revealed.
"Barely I could use my abdominal to move and I was like: 'This is not going to happen'. But I took the flight and suddenly when I landed in Australia, the feeling was a lot better.
"Every 24 hours, I was making a lot more progress than the first seven days, which is actually what all the doctors told me: 'Don't worry, because the second week, every day is going to improve a lot more than the first week.'
"Even Alex Albon told me this, I remember, so it just followed more or less what everyone told me."
Sainz left no stone unturned to speed up his recovery process, including the use of hyperbaric chambers to increase oxygen levels, and a so-called Indiba machine which uses electromagnetic current to accelerate the healing process of his scar tissue.
"As soon as I got my appendix removed, I went on the internet and started talking with professionals and said, 'OK, what helps to speed up recovery?', he detailed.
"From that point onwards, I started doing all the sort of things that you can do to speed up recovery, the wounds, the scar tissue, what you can help to be faster on that. Talking to other athletes, talking to other doctors in Spain, internationally. And then I put together a plan with my team.
"The reason why athletes recover faster is because you can dedicate 24 hours per day for seven days to recovery. And that's exactly what I did.
"I started going to hyperbaric chambers twice a day for one hour, taking an Indiba machine, that is an electromagnetic thing for the wounds.
"I was programming my time in bed, my time to go for a walk, my time to eat, the kind of food that you have to recover. Just everything is centered around recovery to try and be ready for Australia."
Sainz's second part of the race was unknown territory after only being able to do limited long runs in practice, but he said his body held up well even though he was "stiff and tired" by the end.
"Obviously, spending seven days in bed for your physical fitness and for all the muscles, it's just not very healthy for an athlete," he said.
"The second half of the race was a bit of an unknown but once I got up in front and I had a gap, you can manage everything.
"You can choose your places where to push and not to push and everything becomes a lot easier.
"I'm not going to lie, the last five or 10 laps I was a bit stiff and tired, but nothing that was slowing me down too much."
