Mercedes boss Toto Wolff says he cannot rule out the possibility of Sebastian Vettel racing for the marque in 2021, pointing to the situation he experienced when Nico Rosberg retired.
Mercedes currently fields Lewis Hamilton and Valtteri Bottas but neither driver is under contract beyond the end of 2020.
The marque also supports Williams racer George Russell.
It was confirmed last month that Sebastian Vettel will leave Ferrari at the end of 2020, with Carlos Sainz Jr. replacing him, while Daniel Ricciardo will join Lando Norris at McLaren.
Wolff stressed that his current drivers are his priority but pointed to the shock retirement of Rosberg at the end of 2016.
Newly-crowned champion Rosberg was under contract, alongside Hamilton, until the end of 2018, but opted to retire, prompting Mercedes to draft in then-Williams driver Bottas.
“We owe it to a four-time World Champion not to come out and say straight away ‘no’,” Wolff told select media including MotorsportWeek.com on Wednesday. “You need to think about it.
“On the other side, we have a fantastic line-up and I am happy with both our drivers and George, but you never know – one may decide he doesn’t want to go racing anymore and suddenly you have a vacant spot.
“That’s why I don’t want to come out in June and say “no chance, Sebastian” and that he is not racing for us.
“First of all, I wouldn’t do it to him as a driver – to be that blunt – and on the other side, I have seen black swans appearing when nobody expected.
“Remember Nico Rosberg. So in that perspective we are just keeping our options open but of course concentrating our discussions on our current drivers.”
Wolff added that “we were quite surprised on the early movements, as you need to start the season with a driver you know you’re going to lose so it’s very tricky to develop a car without having the driver be part of it.
“Every single driver needs to be a team player as well, and that becomes second priority in my opinion, then for the relevant guy. For us, we want to take our time.
“Our priority lies on the Mercedes drivers, Valtteri and Lewis. George and the Williams situation we’re looking on with interest.
“And beyond that, you need to not discount any driver. That’s why I said I don’t want to discount Sebastian as a four-time World Champion because who knows what happens in the next months.
“If I would have told you in January we would not have any racing in the first half of the year, nobody would believe it. So in that respect, we’re just keeping our options open in that respect.”
