Off-spinner Nathan Lyon took four wickets off six balls to catch Pakistan tottering at 77-5 at lunch on the first day of the second and final Test in Abu Dhabi on Tuesday.
Lyon dismissed Azhar Ali caught and bowled for 15 in his fourth over and then next ball had Haris Sohail caught close to the wicket for nought.
In his next over, Lyon had Asad Shafiq caught at short-leg and two balls later had a dancing down the wicket Babar Azam bowled -- both batsmen failing to score.
At lunch opener Fakhar Zaman was unbeaten on 49 and under-performing Sarfraz Ahmed four not out as Pakistan need a big fightback to post a challenging total after winning the toss.
Lyon has figures of 4-12 in his seven overs.
It was pacer Mitchell Starc who provided Australia an early breakthrough in the third over when Mohammad Hafeez fell to a freakish catch at short leg by Marnus Labuschagne for four.
Hafeez had scored 110 in the drawn first Test in Dubai.
Pakistan made two changes from the first Test, handing Test caps to Zaman and pacer Mir Hamza, leaving out injured Imam-ul-Haq and out of form fast bowler Wahab Riaz.
Australia kept the same eleven from the first Test.