Mercedes have confirmed Pascal Wehrlein and George Russell will share reserve driver duties at the Silver Arrows for the 2018 season.
Wehrlein was unable to find a seat in Formula 1 after being let go by Sauber, but Mercedes have not closed the door on him fully and still have hope in the 23-year-old.
As he is back with Mercedes in the DTM series, F3 champion Russell will share responsibilities after making his breakthrough with Force India in a couple of FP1 sessions last season.
"With Pascal we couldn't find the right solution and he's back in the DTM, but he's our reserve," said Mercedes motorsport boss Toto Wolff. "We will see which options open up."
"And we will see how George is going to go in F2.
"He does a brilliant job for us in the simulator, he has met our expectations in winning the GP3 title, Force India is very impressed by him.
"F2 is the next step. We're keen to see how he's going to perform."