Valtteri Bottas came very close to losing his podium finish in last weekend's Spanish Grand Prix, Mercedes has revealed.
"It's fair to say that it was extremely marginal," chief strategist James Vowles said in the team's latest Pure Pitwall video presentation. "If the race had been a lap or two longer, we could have been in big, big trouble."
Bottas had pitted earlier than planned on lap 19 in an attempt to jump Ferrari's Kimi Raikkonen. He put on a set of medium tyres, but had to complete another 47 laps until the end of the race if the revised strategy was to work.
The team opted not to pit Bottas under a late Virtual Safety Car, as Ferrari did with Sebastian Vettel.
"We concluded based on all the evidence that we had is there was as strong possibility of Vettel [stopping]," said Vowles. "It's extremely unlikely that anything else would have happened if we took it [a second stop].
He said that the call had been for Bottas to stay out, "rather than just staying behind Vettel, and Red Bull, and therefore finishing lower than the P2 that was the potential in the car."
Staying out meant that Bottas duly moved into second place, but it pushed his tyres to their absolute limit.
"The last few laps of the race for Valtteri were very, very tense," Vowles acknowledged. "We knew that the front left tyre would be very much down to zero rubber remaining."
Nor could Bottas ease off, because the Red Bull of Max Verstappen was within striking distance behind him on fresher tyres. Vowles said that Mercedes had been convinced their rivals were "absolutely going to make the one-stop work."
"[Valtteri] had eight seconds of race time relative to the Red Bull behind," he continued. "What we were trying to do was very delicately use up some of that race time.
He explained that Bottas has been required "to slow down in some of the key corner sequences to make sure we looked after that tyre whilst not losing temperature in the rubber that was still actually left on it."
"It's a very, very delicate balance," Vowles added. "I really can't understate this, Valtteri did an absolutely incredible job.
"We put him in a very difficult position, and he dealt with it absolutely perfectly, taking that tyre just to the end of the race as we asked him to do.
"We decided to take the risk," he insisted. "We took the tyres to the end of the race. It was extremely close, it was a very tight judgement call, but it ended up on the right side for us on that occasion."