England ended day two in Rawalpindi with pressure piling up, trailing by 53 after losing three second-innings wickets in nine overs before the close.
They had earlier let a promising position slip as centurion Saud Shakeel (134) lifted the hosts from a shaky 7-177 to 344 all out.
Wicketkeeper Jamie Smith had earlier put him down on 26 and he cashed in brilliantly, sharing partnerships totalling 160 with the tail.
Joining Shakeel in a crucial ninth-wicket stand of 72 was Sajid, whose striking facial hair, provocative celebrations and haul of 16 wickets since being recalled in Multan last week have cast him a central figure in the drama.
This time he hurt England with the bat, too, swelling Pakistan's lead with a frantic 48 not out including four big sixes off spinners Shoaib Bashir and Rehan Ahmed.
Saud Shakeel ground out 134 runs as Pakistan closed in on a series victory over England. (AP PHOTO)
Speaking to local broadcasters afterwards, the antagonist suggested he had outwitted Ahmed and Bashir by announcing plans in his native tongue, which both understand due to their Pakistani heritage, then doing the opposite.
"We were doing that to deceive the bowlers. Rehan and Shoaib understand Urdu, so to fool them, we wanted them to hear that we were only looking for the single," he said.
"When we did that, they brought the field up and the bowlers flighted it. Saud told me once they do that, no half measures, just go for the big shot as hard as you can."
Ahmed refused to give credit to Sajid's ruse, insisting his ploy had fallen on deaf ears, but accepted England found themselves in a difficult position.
"Nah, he didn't fool me or anything. He just said that for the media," Ahmed claimed. "I didn't even hear it, (I think) he said something like he was going to run down the wicket but I knew he was going to try and scoop me, so it didn't really work.
"He didn't really fool me or Bash but he batted well and hit some big blows. Obviously the momentum is with them at the moment but hopefully we can soak it up a bit tomorrow, put it back on them."
After conceding a first-innings deficit of 77, England slumped to 3-24. Sajid was at them again when he had Ben Duckett lbw, with spin twin Noman Ali removing Zak Crawley and Ollie Pope.
They were surely delighted when bad light brought an early end to proceedings but Ahmed, who had earlier taken 4-66, remained optimistic.
"There's no sense of negativity or heads down. Everyone still knows there's a job to do and we can't wait to do it," he said.
"There is so much batting to come and we're still very positive in the changing room. Whatever defendable total we put up, I'm sure we can defend it."
