That is what transpired at Craven Cottage on Tuesday evening when a Leeds line-up including the likes of Kalvin Phillips, Stuart Dallas, Rodrigo and Dan James avoided the ignominy of exiting the Carabao Cup at Championship outfit Fulham, who had changed their entire starting 11 from the weekend.
On his debut for the club from the bench, Scottish youth international McKinstry, 19, scored the fateful spot-kick in a shoot-out which went to sudden death after the game ended scoreless.
Now Yorkshire’s sole representative in the competition, Leeds will travel to Arsenal in round four.
The shoot-out saw another teenage substitute in former Wigan midfielder Gelhardt, also 19, convert on a night when Dallas and Adam Forshaw both missed from the spot for United.
Praising the young duo, James – flown to the capital by helicopter to play after his partner gave birth to a baby boy – said: “I think maybe we were disappointed as we created a lot of chances to go and win the game in normal time.
“But thankfully the boys stepped up and put the penalties in the back of the net.
“All credit to the young boys that came on, they did so well and they stuck their penalties away.
“It’s not easy to stand up, come on for their debut and take a penalty. They maybe thought they wouldn’t have taken one, but you have got to be ready and they certainly were.”
Meanwhile, Huddersfield Town midfielder Lewis O’Brien – a big summer transfer target for Leeds – has signed a new long-term contract and spoken of his relief following a tough summer when speculation was rife regarding his future.
O’Brien, 22, whose deal runs until June 2025, said: “Obviously, summer was a hard time for everyone with all the speculation and news going around.
“But we went about everything how it is supposed to [be] and I never kicked off about anything. It is just the way football works and for me to sign a new deal now, I just think it is the right time and step in my career to go forward.”