Mercedes are considering Fernando Alonso as a replacement for retiring world champion Nico Rosberg.
But two-time championship winner Alonso is about to enter the final year of his three-year deal with McLaren, meaning Mercedes may have to look elsewhere.
"You have to consider Fernando," Mercedes boss Toto Wolff told Sky Sports' F1 Special: Nico The Brave show.
"He is a driver I respect a lot. He combines talent, speed and experience. It's all there.
"But he is in a contract with McLaren-Honda at the moment and we just need to weigh all the other options up."
Mercedes face a race against time to bring in a new driver alongside Lewis Hamilton, with pre-season testing due to begin in February.
Rosberg made his surprise announcement last week, just five days after sealing the drivers' championship.