Pakistan suffered a significant setback when pace bowler Hasan Ali and all-rounder Faheem Ashraf were ruled out of the first Test against Australia through injuries.
Hasan has a muscle strain and Ashraf an injured hamstring and will miss the Test starting in Rawalpindi from Friday.
The Pakistan Cricket Board (PCB) said spinning allrounder Iftikhar Ahmed and fast bowler Mohammad Wasim Junior will replace the injured duo.
"Both Iftikhar and Wasim (chosen due to their all-round ability) will reach Islamabad tonight and start their three-day isolation at the team hotel," said a PCB release.
The pair will join the rest of the squad after clearing covid tests.
Hasan, 27, has been anchoring Pakistan's bowling attack along with Shaheen Shah Afridi in the last 12 months.
He took a ten-wicket haul in the last Test in Rawalpindi, against South Africa in February, before taking nine wickets in Harare against Zimbabwe two months later.
He finished the year with 41 wickets in eight Tests, just behind India's Ravi Ashwin (54) and Shaheen (47).
Ashraf has been a star with both bat and ball, allowing Pakistan to use two spinners in matches.
PCB hoped Hasan and Ashraf would regain fitness ahead of the second Test in Karachi starting from March 12.
The third and final Test is in Lahore from March 21.
Australia will also play three one-day internationals and a T20I on the tour.
Pakistan's revised squad for first Test:
Babar Azam (captain), Mohammad Rizwan, Abdullah Shafique, Azhar Ali, Fawad Alam, Haris Rauf, Iftikhar Ahmed, Imam-ul-Haq, Mohammad Wasim Junior, Nauman Ali, Sajid Khan, Saud Shakeel, Shaheen Shah Afridi, Shan Masood, Zahid Mahmood.