The Spaniard classified fifth in the second running of the Miami Grand Prix last weekend, a result that was not affected by the imposition of a five-second penalty for pitlane speeding.
Meanwhile, team-mate Charles Leclerc - who crashed in Q3 to trigger a red flag - finished where he started in seventh. Both drivers bemoaned a lack of pace on the hard Pirelli tyre.
That lacklustre showing and shunt for Leclerc arrived despite Ferrari sporting a tweaked floor that both drivers initially reported had made the handling of the SF-23 more “benign”.
But the deficient Sunday pace has led Sainz to state the car has “zero flexibility” and that pushing in a stint harms the tyres to leave Ferrari unable to switch strategies mid-race.
Asked by Autosport whether the benefit of the revised floor had continued into the grand prix, Sainz said: “At the moment, I cannot push.
“Especially in the race, as soon as you push for one lap, you do one good fast lap and then the next lap you are 0.3s slower with the tyres that were just very, very tough.
“It means that we don’t have flexibility to push or not push and we just need to follow a certain pace to make it to the end.
“I am surprised as I thought we would be better but [Miami] showed us that we still have some work to do.”
Source: Autosport