England made early inroads with two wickets to keep Pakistan down to 117-3 at lunch on the opening day of the third and final Test in Karachi on Saturday.
Azhar Ali -- playing his last Test -- was caught behind for 45 off pacer Ollie Robinson in the last over before lunch to give England a successful first session.
Skipper Babar Azam, who won the toss and batted on a flat National Stadium pitch, was unbeaten on 30.
Azhar and Azam added 71 for the third wicket after opener Abdullah Shafique fell for eight and Shan Masood 30.
Sensing the pitch will take spin, England started the attack with left-arm spinner Jack Leach, who trapped Abdullah Shafique leg-before in the sixth over of the day.
Masood fell to the trap of short bowling as he pulled fast bowler Mark Wood straight into the hands of deep fine-leg fielder Leach.
Masood hit five boundaries while Azhar had six hits to the ropes.
Hard pressed to avoid their first-ever whitewash in a home series, Pakistan made four changes with Azhar, Masood, Mohammad Wasim junior and Nauman Ali drafted in the side.
England, who won the first two Tests, made two changes from the last match, bringing in wicketkeeper Ben Foakes and Rehan Ahmed in place of James Anderson and Will Jacks.
Rehan, at 18 years and 126 days, became the youngest player to debut for England, beating Brian Close's record of 18 years and 149 days set in 1949.