Akhtar, who was last month cleared of a doping offence, was being sent to South Africa as young pacer Umar Gul had been ruled out for two to three weeks with an ankle injury, a Pakistan Cricket Board (PCB) official told Reuters today.
''Gul has been ruled out and the team management sent a request to the selectors to rush a replacement,'' Ehsan Malik, the board's communications director said.
Akhtar would fly out tomorrow, Malik said.
''There is a problem with the flights schedule or he would have left immediately,'' one board source said.
Pakistan have also lost senior batsman Mohammad Yousuf and allrounder Shoaib Malik for the opening Test.
Yousuf is looking after his ill wife and Malik has been advised to take two weeks' rest to recover from an ankle injury.
Akhtar, Pakistan's most senior bowler with 165 Test and 208 one-day wickets, was not picked for the Test series as the selectors said he needed to regain his match fitness and form.
He and fellow pacer Mohammad Asif were cleared of having intentionally taken a banned substance, nandrolone, by an appeals commission of the board after they had earlier been banned for two years and one year.