At lunch on the second day of this four-day match, Pakistan's final first-class fixture before next week's first Test against England at Lord's, England 'A' were 365 for six after Key, captaining the side, had scored 136 - his maiden century of the season.
Test hopeful Alex Loudon was 29 not out and former England wicket-keeper Chris Read unbeaten on 39, the duo's seventh-wicket stand currently worth 82.
When play resumed Friday Faisal Iqbal, already in the team for this match, continued to deputise for Kamran Akmal, the only wicket-keeper currently in the Pakistan squad, who'd sustained a left index finger injury on Thursday.
England 'A' were 268 for three, with Key 128 not out and Ravi Bopara seven not out on a pitch still good for batting.
Bopara though fell for 15, his forceful cover-drive off Mohammad Sami well caught by substitute Rana Naved, recovering from a groin injury.
Then, next over, 282 for four became 283 for five when Jamie Dalrymple, one of England's few successes in their 5-0 one-day series thrashing by Sri Lanka, was lbw for one to a full length ball from impressive quick Umar Gul.
Abdul Razzaq, with only his second delivery Friday then took the prize wicket of Key, who played the last of his 15 Tests against South Africa at Centurion in January 2005.
The fast-medium bowler made the ball move away from the right-hander, knocking back the off-stump to end Key's innings of more than seven hours.
It was another example of Pakistan's fine bowling on a pitch with little in it for their quicks.
Key, dropped on 30 by Akmal on Thursday, faced 269 balls with two sixes and 17 fours and his exit left England A on 291 for six.
But the 27-year-old Kent captain, playing on his county home ground, could be proud of an innings which if it was unlikely to catapult him into a place in the first Test squad due to be announced Sunday - he is still hampered in his ability to throw after shoulder surgery in the off-season - had revived his hopes of making the Ashes tour later in the year.
Read, who lost his place in the Test side to Geraint Jones because of his Kent rival's supposedly superior batting, hooked and pulled Razzaq with authority although the bowler thought he had him caught behind on six.
Read though was unconcerned, using his feet to go down the pitch to leg-spinner Danish Kaneria and drive the former Essex bowler back over his head for six as skies darkened and rain threatened.
Play was halted at 12pm local time (1100GMT) for Britain's national two minutes silence marking the first anniversary of the London terror bombings, players from both sides lining up on the outfield while spectators stood.