Despite finishing half-a-second ahead of new partner Charles Leclerc in the SF21, Sainz acknowledged he has yet to fully get to grips with the car and lacked familiarity with its characteristics in changeable climates.
"If you compare this [car] to the McLaren, when the wind changed, I perfectly knew what the car was going to do so I could always anticipate myself and always, independently of the conditions, extract 95 to 100 per cent of the car," said Sainz.
"When you switch teams and cars, as soon as the conditions change, you don't know how the car is going to react so you are always underdriving a bit.
"You don't want to do stupid mistakes and you want to stay a bit below the limit of the car because you don't know how the car is going to react.
"I always say you need races, experiences of the car going through different conditions to understand how the car reacts to the wind, temperatures and build a core of experience to know how to adapt to the conditions."
Ferrari is in a recuperation period following a dismal sixth-place finish in last year's constructors' championship, with the team hoping a new power unit this year will complete part of the puzzle in regaining race-winning form.
When asked how hard it was to drive the team forward with such little confidence in the machinery, Sainz conceded: "It is tricky.
"You need to stay mentally disciplined because you don't want to give too many comments about balance because you know you are possibly underdriving a bit.
"I managed to adapt well between the sessions, I managed to feel reasonably at home in the car but tomorrow could be a different story, as soon as the wind changes again.
"If it picks up, it could be a completely different story and I could be starting from scratch again and trying to find my feet little by little. The trick here is to let the sessions go by, let the experience build."
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