The manner of Vettel's win, the second in three races so far this season for the Ferrari man, could force them into picking a number one driver, and asking the other to play back-up to his title bid.
That is what eventually happened in Bahrain, when Mercedes finally - just before half-distance - grasped the nettle and ordered Valtteri Bottas to move over and let Lewis Hamilton by.
By then, it was too little too late. Vettel had a six-second lead and, despite a valiant charge by Hamilton after a late pit stop, the German won by about the same margin.
Afterwards, the mood at Mercedes matched the night skies on the Arabian peninsula, and team boss Toto Wolff was already grappling with his conundrum.
How long before you have to choose one driver to back for the title, he was asked?
"We don't like that," he said. "At all. It is not what we have done the past couple of years. But the situation is different now. So it needs a proper analysis what it means and where we are.
"We'd like to give each of them equal opportunity at the start of the race. We owe it to them. Then you see what we did in the race. We made the call. We made the call twice."
Just as in Australia at the first race of the season, Vettel and Ferrari's victory was based on aggressive strategic thinking and good use of tyres.
The German, third on the grid, jumped Hamilton off the line - as he was always likely to do from the cleaner side of the grid - and slotted into second place behind Bottas.
The Finn had taken his first pole position on Saturday. He overhauled Hamilton after what Mercedes said was a rear-end snap in Turn 10 on Hamilton's final lap, but which Hamilton said after the race was largely because the DRS overtaking aid, which boosts straight-line speed, did not engage between Turns 10 and 11.
Bottas lacked pace in the race. Mercedes said that in the first stint he was hamstrung by high tyre pressures caused by a generator failure on the grid which prevented the team from bleeding out enough air. The result was a five-car queue, comprising Vettel, Hamilton and the two Red Bulls.
With Vettel stuck, but sensing he had a very quick race car, Ferrari took the initiative, pitting him early on lap 10. There was no point Mercedes following him in - they knew whoever they pitted would come out behind
A safety car three laps later gave Vettel what he said was "a heart stop" that he might lose a potential advantage gained in this way for the second week in succession, just as he had in China.
But a slow stop for Bottas, caused by problems with pit equipment, ensured Vettel retained the lead - and Hamilton delivered his own race another blow by driving too slowly on the way into the pits, trying to give the team time to service Bottas and also prevent Daniel Ricciardo from jumping him. It earned him a five-second penalty. Without it, the end of the race would have been much closer.
With Vettel now in the lead, and Hamilton stuck behind Bottas, who was still slow despite corrected tyre pressures, the Ferrari began to edge ahead - 1.2secs at the restart, then 1.6, 2.1, 2.3, 2.7, 2.9, 3.5, 4.1, 4.9 etc. Only when Vettel had an advantage of more than six seconds did Mercedes finally make the call for the drivers to swap positions.
Immediately, Hamilton came back at Vettel, closing to within 4.3secs within five laps before the Ferrari made its second and final pit stop. Mercedes' only hope was to leave Hamilton as late as possible before his final stop. But 19 seconds in 15 laps was always going to be too big a margin to close down. - BBC -