Williams are not close to ending the wait over the identity of their second driver for 2018.
Lance Stroll's place is set in stone, but there are several contenders to replace the re-retiring Felipe Massa.
Swiss newspaper Blick reports that the favourites now are Robert Kubica and Toro Rosso refugee Daniil Kvyat, with the latter said to be promising some important Russian sponsorship.
Also rumoured is that Kubica might be given a one-off chance to prove himself in the Abu Dhabi finale, given that he needs to be guaranteed the entire 2018 season as he forfeits a significant disability insurance payout.
However, Williams boss Paddy Lowe said the team is not ready to make a call.
"We're very unlikely to make a decision in short order," he said in Brazil.
"We have a number of different options and we'll take our time with that and let you know when we have an answer."
Another rumour is that Sauber are poised to announce their 2018 lineup, amid suggestions that Charles Leclerc could even be given an early start in Abu Dhabi in Pascal Wehrlein's place.
"We will do the [driver] announcement, I hope, in Abu Dhabi," team boss Frederic Vasseur admitted.
"I think Charles is doing a good job. The situation in Friday morning practice is not easy but he's always consistent and shows a strong pace."
Williams are fifth in the standings heading into tomorrow's Brazilian Grand Prix.
