Mercedes boss Toto Wolff says the outfit briefly feared that neither Nico Rosberg nor Lewis Hamilton would finish the Russian Grand Prix due to technical issues.
Rosberg dominated from pole position while Hamilton recovered from a set back in qualifying to complete a 1-2 for the team at the Sochi Autodrom.
Mercedes warned Hamilton during the race that he was suffering from a water pressure issue, but Wolff also revealed that Rosberg faced a problem at the head of the pack.
"That race was anything but plain sailing today - it was a pretty stressful experience to get both cars home, and there was a point when we thought neither of them might make it to the flag," he said.
"First of all, congratulations to Nico, he did a perfect job all weekend and controlled the race from the front once again.
"He didn't put a foot wrong and, when we faced an issue on the MGU-K during the middle part of the race, he was able to do all the necessary steps to keep it under control and bring it home.
"As for Lewis, he drove brilliantly. Some really good, aggressive passing manoeuvres and clever racing brought him to P2 - and he was just getting his head down to charge when we saw a water leak and he was losing water pressure.
"The only thing to do was ask him to back off to bring the car home and fortunately that meant the situation stabilised but cost him the chance of racing Nico."