Mercedes bosses Niki Lauda and Toto Wolff admit they would be forced to consider Sebastian Vettel
They eventually convinced Williams to part company with Valtteri Bottas but the Finn was only handed a one-year deal.
And Mercedes are understood to be considering their options for 2018, when Vettel's current deal at Ferrari will expire.
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"[Signing Vettel] is not our plan – I must say that quite clearly," Niki Lauda, former F1 world champion and Mercedes non-executive director, told German newspaper Stuttgarter Zeitung.
But Express Sport understands that Vettel is likely to explore other options this summer if Ferrari are not one of the fastest teams on the grid.
The German four-time world champion has won just three times since joining Ferrari in 2015.
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And Mercedes team boss Toto Wolff refused to rule out making a move for Vettel at the end of the season if he were available.
Sebastian Vettel impressed for Ferrari during pre-season testing in Barcelona
"I personally have a good relationship with him and he would fit into the team," Wolff said.
"However, Sebastian is someone who is absolutely loyal to his current employer.
"When Nico retired, he was not one of the interesting applicants for the seat.
"He only said 'Oh, this is surprising'.
"He is focusing on Ferrari with everything he has.
Valtteri Bottas has signed for Mercedes but his contract is only a year long
"What the future brings we will see, but it would be negligent to not have Sebastian on the list.
"But as good as [Vettel driving for Mercedes] sounds, it matters little now.
"My favourite scenario is that it works out with Valtteri and Lewis."