Sebastien Buemi is not ruling out a return to the F1 grid.
Since losing his Toro Rosso seat, the 28-year-old Swiss has become a top sports car and Formula E driver.
But Auto Motor und Sport said he was back at the wheel of a Red Bull F1 car last week to help Pirelli test tyres at Paul Ricard.
There are rumours Renault advisor Alain Prost is pushing hard for the works Renault team to consider Buemi for the future.
"I don’t know if Alain wants me back in formula one — he needs me in Formula E," Buemi smiled.
The timing of the Buemi rumour is interesting, as Renault is believed to be considering dumping the struggling Jolyon Palmer within this season.
Another potential contender is Robert Kubica, with the Pole stepping up his F1 testing this week with another run in the 2012 car, at Paul Ricard.
The next rumour is that the Pole could then get an outing in Renault’s 2017 car at the post-Hungarian GP test.
"I have not yet driven a current F1 car," Kubica told France’s L’Equipe.
"I could not be ready for Silverstone as it would take me two days of tests in a current car. That would accelerate my chances 1000 per cent."
Renault boss Cyril Abiteboul says it is "too early to say if Robert will be with us in Budapest".