Pakistan 73-3, trail England by 194 after spinner Sajid shines
Sajid finished with 6-128 and Noman Ali grabbed 3-88 after a rearguard 89 by Jamie Smith enabled England to post 267, having stuttered to 110-5 at lunch.
At the close, Pakistan captain Shan Masood and Saud Shakeel were both unbeaten on 16, with the home team still trailing by 194 and the match in the balance.
On a dry and spin-friendly Rawalpindi pitch, 13 wickets fell on day one with all but one going to the spinners.
After the Pakistan spinners' exploits, England's slow bowlers came to the fore in the final session as Shoaib Bashir dismissed Abdullah Shafique for 14 and Jack Leach accounted for Saim Ayub who had made 19.
Gus Atkinson was the only fast bowler to grab a wicket on day one, dismissing Kamran Ghulam for three.
It was wicketkeeper Smith who enabled England to add 149 for their last four wickets.
Smith smashed six towering sixes and five fours in his 119-ball knock before he was caught off a miscued slog against spinner Zahid Mahmood in the last over before tea.
After tea, Sajid removed Rehan Ahmed for nine to complete his third five-wicket haul before also dismissing Leach for 16.
England lost captain Ben Stokes in the third over after the break, caught by Sajid for 12 but Smith, who reached his fifty off 94 balls, and Atkinson (39) added 105 for the seventh wicket.
The morning session was dominated by Sajid and Noman who bowled unchanged for 42 overs.
After England won the toss and batted, Pakistan gave the new ball to the spin duo who benefited from the parched pitch offering turn and low bounce from the first ball.
It was only the fourth time in Test cricket history the new ball on the first morning was taken by two spinners and the first time in Pakistan.
Zak Crawley and Ben Duckett raced to 56 in a confident start but England lost Crawley (29), Ollie Pope (three) and Joe Root (five) in the space of just 24 runs.
Noman had Crawley caught off a miscued drive while Sajid removed Pope and Root leg before.
Duckett, who completed a half-century off 76 balls, was trapped lbw by Noman for 52 after hitting four boundaries and a six.
First Test triple centurion Harry Brook lasted for 14 deliveries before being bowled behind his legs by Sajid for five after he failed to connect on a sweep.
Both the teams included three spinners on a grassless pitch which the hosts dried with fans and heaters in the build-up.
Sajid and Noman shared all 20 wickets in Pakistan's second Test win to level the series at 1-1 after England won the first by an innings, with both matches taking place in Multan.
