Mercedes feared George Russell would not finish Sunday's Brazilian Grand Prix due to a water leak, team boss Toto Wolff revealed after the British driver celebrated his first Formula One victory.
Russell had led a seemingly trouble-free race from the start at Interlagos but Wolff, who did not travel to Brazil, told reporters on a video call that it had been a different story behind the scenes.
"We had a water leak on the car throughout the race and it wasn't clear whether we could actually make it to the end," said the Austrian.
"We all agreed we're going to let him drive to the end even without water, on whatever was there to cool it and just try to finish the race."
A team spokesman said Russell, whose one-two win with seven-times world champion team mate Lewis Hamilton was the first of a difficult season for once-dominant Mercedes, had not been informed.
"We were concerned at one point that we would be four or five laps from the finish and not making it but then it did by the skin of its teeth," he said.
A failure to finish would have been a massive blow for the 24-year-old racer, who has suffered such agonies before with Mercedes.
In 2020 the then-Williams driver could have won when he stood in for Hamilton in Bahrain after the champion was sidelined by COVID-19.
Russell qualified on the front row then and led until the team bungled a pitstop and sent him out on the wrong tyres, forcing him to pit again. He fought back to second when a puncture dropped him back and he ended up ninth.
"He deserved to win in Bahrain and we let him down with the car. This victory makes us happy because he could have had one on the clock two years ago and he didn't and now he has that first victory," said Wolff.