Who will fill Nico Rosberg's driving shoes at Mercedes?
Formula One's newly crowned world champion Nico Rosberg stunned the sporting world on Friday by announcing his retirement from grand prix racing.
Rosberg, who won his maiden Formula One title just five days ago at the championship-deciding race in Abu Dhabi, leaves a vacant seat at Mercedes.
We looked at other runners and drivers who could partner Lewis Hamilton at Mercedes next year.
The four-time champion failed to win a single race in a disappointing year at Ferrari.
The 29-year-old has one more season to run on his current deal, but could an early release be negotiated? The switch to Mercedes will be an appealing one to Vettel and for the German constructor, too.
Vettel versus Hamilton - the two best drivers of their generation - also has the hallmarks of a mouth-watering rivalry.
Like Vettel, Alonso's contract expires at the end of the 2018 campaign.
But the 35-year-old Spaniard, who won the last of his two championships a decade ago, will sense the vacant seat at Mercedes as his ideal get-out clause from McLaren.
A move to Mercedes would also see Alonso team up with Hamilton for the first time since their turbulent campaign together at McLaren in 2007.
The 19-year-old Dutchman is widely seen as the heir to Hamilton's F1 throne, and is highly rated by Mercedes management.
But he is under contract with Red Bull and it seems incredibly unlikely team boss Christian Horner would even entertain the thought of Verstappen jumping ship to their biggest rivals.
A member of the Mercedes junior programme, and a driver who has filled in for both Rosberg and Hamilton in testing, but hardly set the world alight during his debut campaign with Manor.
Could Mercedes however, offer the 22-year-old German a one-year deal with the team until Vettel or Alonso become available in 2018?
The Finnish driver recently re-signed for a fifth consecutive year with Williams, but Mercedes might be prepared to offer the British constructor money and Wehrlein in a move to land Bottas' reliable services.
Another young driver who has risen through the Mercedes ranks. Made his grand prix debut alongside Wehrlein at Manor this season, but recently agreed a deal to join Force India, who are backed by Mercedes power, for next season.