With two seats up for grabs in 2019, Toro Rosso could look to two ex-drivers as advisor Helmut Marko admits a long list of options.

In recent weeks, the possibility of a shock return for Daniil Kvyat has been touted and confirmed and now former Formula E champion Sebastien Buemi, who raced with the junior Red Bull team until 2012, is another name linked.

The suspicion was raised after Toro Rosso tweeted a photo of the Swiss, who still has the role of reserve driver at Red Bull & STR, having a seat fitting at their Faenza factory on Thursday.

While purely hypothetical, there could be some logic behind Buemi making a return based on his performances in Formula E and also with Toyota in the WEC.

An all-new line-up is considered likely as Pierre Gasly heads to Red Bull and pressure builds on Brendon Hartley to perform with Marko claiming a "significant" improvement is needed.

Commenting on the driver situation at Toro Rosso for next year, the Austrian added there was no shortage of names.

"There is no shortlist, it's more like a long list," Marko told Speed Week. "There are 10 names on it."

With their lead academy driver Dan Ticktum still some way off building the necessary points for an F1 superlicence, it is necessitating Red Bull's need to look elsewhere.

Lando Norris was a name mentioned earlier in the year, and now the man he'll replace at McLaren, Stoffel Vandoorne, has been recommended by CEO Zak Brown.

Robert Kubica is another but the Pole insists his attention is solely at Williams and then there's Esteban Ocon, who is facing the axe from Force India and now, could be released by Mercedes as teams point to his association as a reason not to hire the 21-year-old.

As Marko concluded: "Everything is possible!"