When the safety car came out after the Antonio Giovinazzi/George Russell accident those in the second half of the field had the opportunity to pit on that lap, and Leclerc duly came in.
However, the team knew that it would be a slightly longer long stop, as the Monegasque driver had an issue with his pneumatic system, which needed an air refill – a procedure that all teams practice and are prepared for.
"F1 engines use air to operate the valves which, as is the case with the oil, can occasionally consume more than normal," said Ferrari head of strategy Inaki Rueda.
"The air bottle on the car can be topped up by connecting it to the compressed air system and in the case of the SF1000, the connector is on the left-hand side. That's why on TV we saw a mechanic attach to the car a sort of jack with a compressed air bottle.
"These things happen from time to time and we practice these procedures over the course of the race weekend."
The complication for Ferrari was that it would normally want to stack its drivers in a safety car situation, and service Leclerc and Vettel at the same time.
However, knowing that Leclerc's stop would be longer than usual the German was told to complete an extra lap before pitting.
"A double stop would have penalised Sebastian," said Rueda. "Which is why he stayed out for one more lap. It meant that Charles lost a place to [Kimi] Raikkonen because of topping up the air, so that Seb was now in front of his teammate."
Leclerc was told of the delay when he drove into his pit box, and he expressed his frustration when he left, saying "Ah come on, for f**k's sake", without realising that his radio was still on.
Both Ferrari drivers were given hard tyres and were thus able to run to the flag, but eventually the team opted to give Leclerc a second stop for fresh tyres so that the pneumatic system could be topped up again.
"We put hards on both cars thinking it was the best option at the time for having a one-stop race," said Rueda.
"But we did not know – and neither did the other teams – how this compound would hold up towards the end.
"Seb had a pretty lonely race to the flag, hoping that those ahead of him would suffer with a performance drop or make a second stop.
"Unfortunately, neither of those two scenarios occurred. With Charles we also had the air problem, as his consumption increased again, although not to a dramatic extent.
"In the position in which he found himself, a second stop seemed a possibility, both in order to make the most of a set of new mediums and also to avoid the risk of having an air problem in the final laps."