Brendon Hartley and Pierre Gasly have been locked in at Scuderia Toro Rosso for the rest of the season, according to reports.
STR called up Hartley to fill in for Gasly at last weekend’s United States Grand Prix while the Frenchman went to Suzuka to try and win the Super Formula championship.
Gasly had only replaced Daniil Kvyat two races earlier when the Russian was dropped, only for Kvyat to return to the line-up at Circuit of the Americas when Carlos Sainz Jr. began his loan spell with Renault.
STR announced earlier this week that Hartley and Gasly would be its two drivers in Mexico, but provided no further advice.
According to Autosport, that line-up will remain unchanged for the last two races in Brazil and Abu Dhabi as STR looks to finalise its 2018 driver plans.
Gasly, who missed out on the Super Formula title when the finale was cancelled because of the threat of a super typhoon, is expected to get the seat full-time next season after impressing in Malaysia and Japan.
It is believed Kvyat has dropped behind Hartley in the race to claim the second seat in 2018, with STR and Red Bull keen to use the next three races to confirm recruiting him full-time is the right call.
Gasly and Hartley, who finished his debut grand prix 13th at Austin, remained coy on their futures when speaking to reporters at Mexico City on Thursday.
“There is not much I can comment on,” said Hartley.
“I’m pretty focused on this weekend, putting everything I learned from Austin into practice.
“There’s going to be a bit more pressure, people will be expecting a bit more, but I’m feeling optimistic and confident I can do the job.”
Gasly added, “It doesn’t change what will happen this weekend. This is my focus at the moment.”