Pakistan are waiting to discover the extent of a knee injury suffered by spinner Yasir Shah.
Yasir was a notable absentee when the tourists named their side for the final Test against South Africa at the Wanderers on Friday.
The Pakistan Cricket Board (PCB) later revealed that the prolific 32-year-old tweaker has suffered an injury setback.
A PCB statement said: "Leg-spinner Yasir Shah has been sent to a Johannesburg hospital for a knee scan.
"Further updates would be provided in due course."
Yasir took just one wicket in the first two Tests as the Proteas wrapped up the series with a match to spare.