Dr Helmut Marko has admitted that Pascal Wehrlein is on the list of contenders to be Daniil Kvyat's teammate at Toro Rosso next year.
Pierre Gasly is moving on to Red Bull Racing, but Brendon Hartley's place at the energy drink company's junior outfit is not secure for 2019.
"The results don't exactly show it, but I know I've got stronger at every race," said the New Zealander.
"I'm just focusing on doing the best I can one race at a time and hoping that I'm on the grid next year."
Dr Marko, in charge of the Red Bull driver programme, admits the list to potentially replace Hartley is long.
He joked to Germany's Auto Bild that, when "arranged alphabetically", former Mercedes protege Wehrlein's name is "very far down" the list.
Plenty of other drivers are rumoured to also be on the list, but a new favourite has now emerged.
His name is Alexander Albon, a Briton with a Thai heritage who is currently second overall in Formula 2.
The 22-year-old has historical links with Red Bull, and according to Auto Bild, he has reportedly driven Mercedes' F1 simulator at Brackley this year.