Ferrari boss Mattia Binotto believes the team's decision in Monaco to call its drivers in for their first pit stop was ill-timed and the tyre switch should have been made either earlier or later.
Leclerc and Sainz enjoyed a commending lead in the first part of the race over their Red Bull rivals when track conditions started to improve and the Scuderia began devising its next step.
While Red Bull brought Sergio Perez in first for a set of intermediate tyres, radio communication between Sainz and the Ferrari pitwall suggested that the Italian outfit's drivers might forego a stint on the inters and switch directly to the hard tyres.
However, Leclerc was then brought in for inters and undercut by Perez, while Sainz remained out on track. On lap 30, the Spaniard finally pitted and took on a set of hards, but Ferrari also called Leclerc back in amid a fair amount of confusion, with the Monegasque arriving just as his teammate was being serviced.
The end result was catastrophic for Leclerc who went from leading the field to fourth behind Perez, Sainz and Verstappen in a handful of laps.
Binotto owned up to Ferrari's strategic blunder which he believed started with the team underestimating the pace of the intermediate tyre.
"I think we need to admit that if you're leading the race, and you're finding yourself in first position, then we may have done something wrong," he admitted.
"So we made certainly mistakes in our judgement and we made mistakes in our calls.
"Now, what's the process which brought us to make mistakes? I think the first mistake was underestimating the pace of the intermediate and the gap we had to the other cars, in terms of track position.
"I think we made a mistake as well, because we should have called him [Leclerc] earlier - at least a lap earlier, or if not, as we did, we should have stayed out and simply stayed on the extreme wet protecting the position and then maybe switching directly onto the dries.
"Now that we made mistakes, I think it's straightforward. What was the process bringing them that brought us to that? It will take some more time to look at it and have a clear explanation."
After the race, Sainz said that he was ready to pick up the mantle from Leclerc and could have won but for finding himself stuck for half a lap behind the Williams of Nicholas Latifi after his switch from wets to hards.
But Binotto refrained from putting his team's defeat on bad luck.
"No, we don't think we have been unlucky," he said. "There is not a matter of being lucky or unlucky. I think we made mistakes in our judgements.
"When you're leading the race here in Monaco, you should be in position, if not keeping the lead, at least finishing second.
"Finishing fourth is showing that we made something wrong. I don't think it's a matter of being lucky or unlucky."
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