With Mark Webber's contract at Red Bull Racing set to expire, it is now strongly rumoured that fellow Australian Daniel Ricciardo is in pole position to replace him.
That would leave a vacancy at Red Bull's second F1 team, Toro Rosso.
The obvious favourite for that seat is Antonio Felix da Costa, a 21-year-old from Portugal.
Currently a frontrunner in the Formula Renault 3.5 series, da Costa has already been drafted into Red Bull's F1 programme, replacing Sebastien Buemi as reserve driver in China while the Swiss was racing sports cars in the UK.
And it seems likely da Costa will be the Red Bull and Toro Rosso reserve once again in Singapore, when Buemi will be racing in the US.
"I am very happy with this strategy," the Portuguese told APA news agency.
"This is a key year -- we're very close to Formula One now and my goal is clearly to be there next year.
"For this I want to win the (Renault) world series. The timing is perfect and I feel very well prepared."
Da Costa is, however, already trailing three drivers in the points standings, including McLaren youngster Kevin Magnussen and Caterham driver Charles Pic's brother Arthur.
As ever with Red Bull's junior programme, then, the pressure is on.
"After a weak season (with a junior driver)," Dr Helmut Marko warned this week, "we end the cooperation."
Da Costa said: "I have had to deal with pressure from day one. It only makes me faster."