Although both Mercedes drivers' contracts are due to expire at the end of the season, team boss Toto Wolff insists he is not yet considering replacements from elsewhere.
Lewis Hamilton is expected to sign a new contract with Mercedes in the near future, but negotiations appear be dragging on and there is no news of when a deal will be announced. Meanwhile, teammate Valtteri Bottas is on a single-year contract and faces a crucial few months as he tries to convince Mercedes to keep him beyond the end of the year.
The driver market for 2019 has the potential for big changes among the top three teams, with Daniel Ricciardo keeping his options open now his Red Bull contract is coming to an end and Kimi Raikkonen also out of a Ferrari contract at the end of the season.
But Wolff says he is only considering F1 drivers that are already under a Mercedes contract -- which includes Hamilton, Bottas and Force India driver Esteban Ocon -- for the time being.
"We are not looking at drivers outside of Mercedes at the moment because, first of all, we need to give our support to our two guys, that's the priority," Wolff said. "It's like if you're happy with your wife, you don't look elsewhere! We are with our two wives -- or three [including Ocon] -- and we are not looking at that.
"Give us a few more races, [let us] start the European season properly, go to Canada, and then the intense July, and I will have a better view."
Alongside Ocon, who is now in his second full season with Force India, Mercedes also has Formula 2 driver George Russell under contract. Ocon's deal with Force India is tied in with the team's engine and gearbox deal with Mercedes, but with Russell knocking on the door of F1 and Bottas and Hamilton occupying the two seats in the factory team, Mercedes could struggle to ensure all its drivers find a suitable drive in 2019.
"It's a good problem to have," Wolff said. "We are very satisfied with how Valtteri has been going these days and Lewis we don't need to talk about -- he's the best of the current drivers in my opinion and then you have these kids growing up like Ocon and George. I am optimistic about the future Mercedes line-up."
As for Hamilton, who Mercedes is determined to retain for 2019 and beyond, Wolff insists the delay in the new contract is purely down to the busy schedule of both team and driver.
"We haven't talked now for a few days or few weeks because it was so intense in getting our act together with the team and all our priority has been concentrated on that, and this is what we do. We are very well aligned in what we expect from each other in the future and it's just finding the time to sit down."