Toro Rosso's 2019 driver line-up is unlikely to be confirmed until December, team principal Franz Tost has revealed. While Daniil Kvyat's return to the team for next year was announced in September, the identity of his partner remains mostly a mystery.
With Pierre Gasly stepping up to Red Bull next year, Brendon Hartley still has a fight on his hands in order to keep hold of his seat.
The Kiwi has been challenged by Tost and Dr Helmut Marko to get the better of Gasly in the final races of the season in order to prove himself – he finished three places ahead of his teammate in Austin last time out.
However, with Formula 2 contender Alexander Albon heavily linked with a return to the Red Bull programme, Hartley still has plenty to prove.
"He showed a good race in Austin. But nevertheless, if you look at the results, he has four points, Pierre has 28 points," Tost said of the two-time WEC champion.
"That means he has to improve his performance if he wants to stay in the team.
"First of all, you have to finish the season to get a clear picture. Then, I assume in December, Red Bull will decide the driver line-up of Toro Rosso."
Hartley says he still has a contract with the team for 2019 and is determined to see it through.
"Nothing's changed from what I've been telling you. My contract is still valid for next year, so nothing changed from one week ago," Hartley said.
"I still believe I'm doing a good job, and when given the equal opportunities, I'm competitive against my teammate which in the end is what you're asked to do in Formula 1.
"I'm looking forward to the next three races and hopefully having another couple of good results like I did in the last few races."