Pakistan captain Shan Masood admitted England taught his team a "harsh reality" on how to win a test with their massive innings and 47-run victory in Multan on Friday.
England's attack made short work of the last four Pakistan batters on day 5, dismissing the hosts for 220 and drawing first blood in the three-match series.
England found a way to win despite Pakistan's first-innings total of 556, responding with the fourth-highest test score of 823 for seven in response.
"It can't be more disappointing than this," said Masood who has lost all six tests since being appointed captain last year.
"England taught us the harsh reality on how to find a way to win a test match which we couldn't find," said Masood who scored a hundred to set up Pakistan's first innings.
"After two days being under the sun and being 556 behind, they gave themselves a chance to bat and scored big and when they came back with the ball they had a plan and they executed that well."
Harry Brook smashed 317 and Joe Root a record-setting 262, giving England a 267-run lead and both players their highest test scores.
Chris Woakes then dismissed Abdullah Shafique with the first ball of the second innings before Jack Leach led the England attack to victory with figures of 4-30.
Masood said England proved themselves a quality side.
"The harsh reality in test cricket is that no matter what the pitch is, quality sides will find a way and England did that and for us the learning is to find a way to win tests," said Masood.
Pakistan's batting has been stumbling due to a slump for talisman Babar Azam, who has gone without a half-century in his last 18 test innings.
"There is no doubt that Babar is Pakistan's best batsman," said Masood of Azam who scored a scratchy 30 and five in the match.
"You always believe that your best batsman is just one innings away and we hope that he returns to form soon."
Meanwhile, spinner Abrar Ahmed remained doubtful for the second test in Multan starting on Tuesday.
"The condition of Abrar is not good so we all pray that he recovers well and plays cricket again," said Masood of the spinner who did not take the field on the last two days due to a high fever.
The third and final test is in Rawalpindi from October 24.