MEXICO CITY -- Toro Rosso will not make a decision on the future of Brendon Hartley until after the conclusion of the current Formula One season.
Last month Toro Rosso confirmed the return of former driver Daniil Kvyat for next season but the identity of his teammate remains uncertain. Pierre Gasly, Hartley's current teammate, is moving up to Red Bull next year to replace Renault-bound Daniel Ricciardo.
Hartley's future has been unclear for a while. He has scored just four points this year but returned to the top ten at the U.S. Grand Prix, albeit after disqualifications for Esteban Ocon and Kevin Magnussen.
Toro Rosso boss Franz Tost wants to see more from Hartley before the season is out.
"He showed a good race in Austin," Tost said. "But nevertheless, if you look at the results, he has four points, Pierre has 28 points. That means he has to improve his performance if he wants to stay in the team."
When asked how long Hartley had left to convince the team he was worthy of another year, he replied: "Of course, 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."
The leading candidate to replace Hartley is Thai-British driver Alexander Albon, 22, who is currently second in the Formula 2 championship after claiming four wins this year.
Albon recently fuelled speculation of a move to Formula One by skipping Formula E's pre-season test, where he had been scheduled to appear with Nissan after signing a three-year deal.
Tost confirmed Red Bull is in talks with Nissan about Albon's contract but said the negotiations will remain confidential.