Brazilian driver Felipe Massa has pulled out of the Hungarian Grand Prix due to illness and will be replaced by reserve Paul di Resta for qualifying later Saturday and for Sunday's race.
The Williams team said in a statement that the 36-year-old Massa went to the Formula One medical centre and then Honvedkorhaz hospital on Friday for "precautionary tests" after feeling "unwell and dizzy" during the second practice session.
Although he was cleared to take part in Saturday's third and final practice run, he again felt unwell and made the decision to withdraw after clocking the 17th time out of 20 drivers.
Williams says it "supports Felipe's decision and the team will work with him to ensure he makes a full recovery, with a view to returning to the race track for the Belgian Grand Prix" in late August.
Di Resta will race alongside 18-year-old Canadian driver Lance Stroll.
For the 31-year-old Di Resta, it is an unexpected chance to get back behind the wheel in F1. The last of his 58 F1 races was the Brazilian GP in November 2013.
In three seasons with the Force India team, he had the best result of fourth at the Singapore GP in 2012 and at the Bahrain GP in 2013.