Valtteri Bottas is out of the Australian grand prix.
The Finn spent the night in the nearby Alfred hospital after suffering back pain during qualifying in Melbourne on Saturday.
He is at Albert Park on Sunday, but was missing from the official driver group photograph on the grid and the subsequent driver parade.
It is rumoured Bottas, who was seen still walking gingerly, failed the FIA’s mandatory car extraction test, which requires a driver to be able to get out of the car and replace his steering wheel within a specified time.
"Following a series of tests, the FIA medical delegate has deemed Valtteri Bottas unable to race today," said Williams an hour before the race.
"The team respect’s the FIA’s decision."
In a media statement, the British team said Bottas has suffered "a very small tear in the annular part of a disc in his lower back".
Williams will now "work with Valtteri ahead of the Malaysian grand prix to ensure he receives the treatment required to get him back to full fitness".