Valtteri Bottas remains in doubt for Sunday’s Australian grand prix.
The Finn spent the night in the local Alfred hospital, after he was seen receiving assistance to emerge from the cockpit of his Williams after qualifying.
Bottas, 25, is at Albert Park on Sunday, but Williams confirmed he is suffering from a "bad injury".
"Valtteri had sustained some soft tissue damage in his lower back," said the team.
"(He) is now working with a physiotherapist prior to final assessment by the FIA in the early afternoon to determine whether he will be able to race later today," Williams added.