The former BMW and Renault driver admitted to Italy's La Gazzetta dello Sport that he sorely misses F1.
"You do everything to get there and to stay there, then from one day to the next, for reasons that we know, you lose the ability to be there," said the Pole.
"So it's logical that I miss F1," he added.
For now, the 28-year-old insists he needs to be content with his highly-competitive foray in the second-tier world rally championship with Citroen.
"I still don't have enough mobility in my right arm (for F1)," admitted Kubica.
"There's still a long way to go and not everything depends on me. I would not be in perfect physical shape to race in F1," he added.
He admits, however, that he is now a regular in Mercedes' F1 simulator at Brackley, while the German team has admitted he is assisting with car development.
But Kubica said: "In reality, I couldn't drive on all the circuits. Monte Carlo for example, you have to turn the steering wheel more and I couldn't do that.
"For sure I could drive the car, I feel as though I'm driving as before on the simulator, but it's pointless to do a (track) test if I can't go on all the circuits."
He is also quoted by Autosprint: "In terms of physical effort, of course the simulator is not able to reproduce the G-force, but the effort behind the wheel and the controls are identical to the real cars.
"Even now I'm using it without any help, but in all honestly I think I would be able to drive only on about 80 per cent of the circuits."
Kubica repeated his denial that an actual return to a F1 test track is already scheduled.
"Because," he smiled, "you could not keep that secret from everybody.
"No, really, without the prospect of racing, a test doesn't interest me," he added.