Saud Shakeel's too-close-to-call dismissal cost Pakistan the match, skipper Babar Azam said after their narrow 26-run defeat in the second Test against Pakistan in Multan on Monday.
Chasing 355 to stay alive in the series, Pakistan were in the hunt with Saud guiding the hosts to 291-6 in the morning session on Day four.
Saud was on 94 when he gloved a Mark Wood delivery down the leg side and Ollie Pope dived to his right to collect the ball.
On-field umpire Aleem Dar adjudged the batsman caught behind in his soft signal before referring the decision to TV umpire Joel Wilson.
Replays could not confirm if it was a clean catch, and the original decision was upheld at a critical point in the see-saw contest.
"The Shakeel dismissal cost us," Babar told reporters after England clinched the series with a match to spare.
"It looked to us as if the ball had touched the ground.
"As a professional, you have to respect the umpire's decision, but we felt the ball had been grounded."
Pope had no ambiguity either about the catch he took to turn the match on its head.
"I didn't think it had bounced before," said the 24-year-old.
"As a keeper, when you've got the gloves on you honestly can't tell. I didn't think it had touched the ground after. When you have gloves on you feel it go in but that's it."
England registered, with a match to spare, their first series win in Pakistan since 2000-01 and captain Ben Stokes put the achievement in perspective.
"Coming to the subcontinent, it's always a tough place to come and win," Stokes told Sky Sports.
"We know what we've achieved this week. We know that it's something that's not unheard of, but very rare to do, especially as an English team.
"We do understand how special an achievement this is this week, but as we keep saying, these series victories and these wins are part of a much bigger picture in what we're trying to achieve at the moment."
