Speaking earlier this month, Red Bull racing consultant Helmut Marko made clear what Brendon Hartley has to do in order to retain his seat at Toro Rosso next season. "Beat Gasly," said the Austrian.

While the kiwi has made a few mistakes this season, his confidence and self-belief has not been helped by his team approaching McLaren for the services of Lando Norris just three races into the season, or recent overtures to F2 star Alexander Albon.

Nor, following confirmation that Red Bull will use Honda engines next season, has the two-time WEC champion's cause been helped by being used as a guinea pig in preparation for next season, and while teammate Pierre Gasly has been similarly affected it could be argued that he is basically doing research ahead of his own switch to the Austrian team.

Asked when an announcement on his team's line-up can be expected, Toro Rosso boss Franz Tost told reporters: "First of all, we have to finish the season to get a clear picture and then I assume in December Red Bull will decide the driver line-up of Toro Rosso."

Asked specifically about Hartley's hopes, Tost said: “He showed a good race in Austin. But nevertheless, if you look to 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."

Asked if talks were continuing with Nissan in terms of Albon, who is due to partner Sebastien Buemi in Formula E in the forthcoming season, Tost replied: "Of course, but you know negotiations are confidential. I can't give any details about this."

The Faenza team has already confirmed that Daniil Kvyat is returning to the fold next season, the Russian having previously been dumped twice.

In today's sessions for the Mexican Grand Prix, Hartley finished ninth and sixth, albeit having sole use of the new front wing and floor that was only available to Gasly last week.

Check out our Friday gallery from Mexico City, here.