Sir Alex Ferguson revealed that Federico Macheda's hat-trick for the reserves against Newcastle last week persuaded him he was ready for a place on the bench.
The Scot challenged the young Italian by saying that if he performed at Newcastle he would get his first team chance on Sunday against Aston Villa.
The 17-year-old responded in spectacular style and boosted his tally to 10 in 16 games for Ole Gunnar Solskjaer's youngsters.
Ferguson was true to his word and Macheda made it a debut to remember when he came off the bench to curl an emphatic shot around Brad Friedel in the 93rd minute to seal a crucial win.
"I got Ole to tell him last Monday he might be on the bench yesterday," Ferguson said.
"He scored a hat-trick.
"That formed part of my decision to bring him on ahead of Danny Welbeck. To play under pressure in front of 76,000 is a big ask.
"But I have seen him in training and at reserve team games and how he handles certain situations.
Worth the wait
"But young players get challenged at this club. It was a late goal but for one like that you would wait until the very last kick because it was so good."
The 67-year-old boss now has the task of keeping the former Lazio youngster's feet on the ground but it is something he has grown accustomed to over the years.
"Everyone likes to read nice things about themselves," he added.
"But you need a certain kind of attitude to deal with all the adulation. The good thing is there are plenty of examples of that with all the players we have had at Manchester United.
"It is part of their make-up."