"Polly could still play in the Test because Morkel needs a fitness Test on Sunday after he developed a niggle in his left foot," coach Mickey Arthur said after the tourists drew a three-day match against the Patron's XI.
The 34-year-old all-rounder Pollock on Friday said he was disappointed over being told by Arthur that he would not be part of the team against Pakistan in the first Test starting here Monday.
Morkel, who bowled only seven overs without taking a wicket in the tour match, stepped on a pebble on the popping crease and hurt his left foot.
Arthur said the injury would be assessed by the team physio later Saturday and Sunday.
The 22-year-old Morkel made his Test debut against India earlier this year and is tipped to take over from Pollock.
Pakistan will also be without their experienced batsman Inzamam-ul Haq, who opted not to play the first Test.