South Africa will assess Vernon Philander's condition before he is cleared to continue in the third Test with England after the seamer spent the night in hospital.
Philander took 2-32 from his 17 overs in England's first innings at The Oval but left the field during Friday's play due to a viral infection.
In his absence the Proteas eventually bowled the hosts out for 353 on day two, Ben Stokes proving a thorn in their side with a crucial 112.
South Africa's reply offered little to be encouraged by as they crumbled to 61-7 in the 27th over, and they reached the close 126-8 with Philander the only man yet to bat.
Whether he will bat on Saturday remains unclear after South Africa team manager Dr Mohammed Moosajee confirmed Philander would spend the night receiving medical attention.
"Vernon Philander has been admitted to hospital and is being treated for a probable viral infection," Moosajee said on Friday.
"He will remain in hospital overnight on intravenous fluids for rehydration and will be reassessed in the morning to determine his participation in the current match."