Valtteri Bottas could sit out the Australian grand prix.
The Finn, who qualified three places behind his Williams teammate Felipe Massa on Saturday, was seen limping in the paddock immediately after the session.
Engineer Rob Smedley confirmed he began complaining of lower back pain during qualifying.
Williams said the 25-year-old driver went to be "checked by FIA doctors".
Shortly afterwards, it emerged he had gone to hospital for further tests.
Asked if Bottas might have to sit out Sunday’s Australian grand prix, a spokeswoman for the Grove based team admitted: "It could go either way."