The German was running in 10th place when he was told there was a pit stop window as other drivers were stopping for a second set of intermediates.
Asked on lap 36 if he might want to try soft tyres should slicks become an option Vettel responded, “Medium, medium, let’s go for it. These inters can’t be any worse.”
The team confirmed that he should box and he came straight in.
However he almost lost the car as he accelerated out of the pit exit, and immediately realised his mistake.
Having twice gone off the road on his out lap and lost a lot of time he was called back in for fresh intermediates, losing more ground with a half-spin in the pit entry.
He tumbled down the order and was eventually classified 18th, ahead only of Haas drivers Mick Schumacher and Nikita Mazepin.
“He wanted to gamble himself, we didn’t tell him no,” Szafnauer told Autosport.
“Seb came on the radio and he said, ‘I want dry tyres, put mediums on,’ and we didn’t challenge him, we did what he said. It happened pretty quickly, so we didn’t debate that long with him.
“Oftentimes we say that in drying conditions like that, it’s a driver’s choice. And we went with that.
“The other way round it’s more of a team thing, but on a drying track the driver’s out there feeling it.
“It’s just I think this track here is a normal drying track, it doesn’t dry normally so it’s hard to predict.
“He knew right away the grip wasn’t there, so he came in the next lap, but he lost a lot of time.”
Sebastian Vettel, Aston Martin, on the grid
Photo by: Glenn Dunbar / Motorsport Images
Asked if the team had any regrets given that a top 10 finish was potentially lost Szafnauer said: “You have to trust him, and the other thing you got to trust is he is good in the wet and tricky conditions, and that’s exactly what was out there.
“So if he says I can do it then who are we to argue? But I think this wasn’t the norm, it’s a different track in the wet.
“Should have, could have, would have, had it worked and he finished fourth or on the podium we would have been happy. So no risk, no reward.
“It wasn’t just the one extra pitstop, because the pit loss is around 20 seconds around here, but it was the extra 30 seconds he lost on that lap and that’s what killed him.
“On the intermediate he did really good lap times once he got through the graining phase.”
Meanwhile Vettel’s team mate Lance Stroll earned two points with ninth place, having passed non-stopper Esteban Ocon in the closing laps.
“A good solid performance, he had good lap times all race. I think we pitted him at the right time. We had a bit of a slow stop unfortunately, and it’s hard to tell where he would ended up. [Carlos] Sainz was pretty quick once he got through the graining phase. But so was Lance, so good performance.”