Debutant pace bowler Saqib Khan grabbed two wickets as Sri Lanka struggled to 114 for three by the end of day two of the opening test after Pakistan declared at 434 for nine in Rawalpindi on Tuesday.
Saqib dismissed Dinesh Chandimal for one in his second over and then removed a well-set Lahiru Udara for 42 to leave Sri Lanka on 65 for three.
His experienced pace partner Mohammad Abbas took the first wicket, having opener Pasindu Sooriyabandara caught behind for a duck in the third over.
Kamindu Mendis (40) and Dhananjaya de Silva (22) were unbeaten at the close, with Sri Lanka still trailing by 320 runs on the first innings.
Bad light again stopped play 25 minutes before schedule.
De Silva was dropped by spinner Arafat Minhas in the penultimate over of the day.
Saqib had the figures of 2-54, while Abbas took 1-23.
Pakistan middle-order batter Saud Shakeel earlier missed his century by seven runs, a miscued hook off Asitha Fernando giving wicketkeeper Kusal Mendis his fifth catch in the innings.
Shakeel, who became Fernando's 100th wicket in 29 tests, hit nine boundaries in his 199-ball innings.
He lifted Pakistan from 281 for five overnight with a resolute 96-run stand with Ghazi Ghori for the sixth wicket. Ghori scored a confident 48.
Debutant Minhas made a stylish 52, the fifth half-century of the innings, that included nine boundaries and a six.
Sri Lanka had hoped for early wickets but struggled on a seemingly hard and green pitch, despite taking the second new ball after 80 overs.
Dilshan Madushanka finally made the breakthrough when Ghori edged him to gully, where Sooriyabandara held a low catch.
Pace bowlers Fernando and Madushanka were the pick of the Sri Lanka attack, both taking three wickets.
The second and final test is in Lahore from 17 November.