Pascal Wehrlein looks to be focused on returning to formula one in 2019.
The German lost his seat at Sauber at the end of last year, and now he is escaping from his Mercedes contract in a move interpreted as preparation for a potential Toro Rosso drive.
Wehrlein recently tested the Formula E car of the new Mercedes works team, but team boss Ulrich Fritz says the 23-year-old is not in the running for a contract.
"Pascal did well in his test but at the time we wanted to make the decision, Pascal’s focus was very clearly on returning to F1," Brazil’s Globo quotes Fritz as saying.
"I can understand that but I do not want to set up a team where a driver says after two races that he is leaving to enter F1. Our expectation was that Pascal would decide in favour of Formula E for the long term," he added.
The only real remaining vacancies on the 2019 grid are at Toro Rosso and Williams.