Brian Barry-Murphy said the decision to take off Omari Kellyman off after 35 minutes in the win over Exeter City was pre-planned as they wanted to avoid any "risk" of overdoing it on his Cardiff City debut.
For Barry-Murphy, the ploy to take him off paid off, with Troy Perrett, along with fellows youngsters Tanatswa Nyakuhwa and Dakarai Mafico, impressing on first-team duties.
"I want them to be really clear that these players, when they come into the dressing room, what it looks like and what's expected of them," Barry-Murphy said of the youngsters in the win over League One rivals Exeter.
"And I want the other members of the squad to show them that. Those players have responded really positively.
"Also Troy, coming on at such an early stage of the game, to make sure we didn't take any risks with Omari, was also very involved in the game.
"I think it's always important to remind ourselves that a competition like this can be overlooked, but it can give someone like Troy a first taste for playing for our club.
"To play in front of so many supporters at such an early stage in his career is exciting for him."
Perrett was one of the standouts in the win, playing over an hour as reward for his excellent form for Darren Purse's under-21s side.
The midfielder, 18, has been at City since he was seven and there were reports a few months back that Aston Villa were eyeing him.
But, confirming the substitution was pre-planned, Perrett himself said he was delighted to get the opportunity and was determined to make an impression.
"I obviously knew I was coming on at that time.," Perrett said post-match.
"I'm just glad to see that the coaches trust me to play a big part in the game and hopefully I showed what I could do on the pitch.
"You always want to make an impression. Getting in and playing my first game is always important and I want to make an impression as it goes on.
"I've grown up with some of the boys and they are getting opportunities. It's good to see the club trusting young players. Hopefully we will see more of that in the coming years.
"It's a great time to be at the club. You see some at the club coming from the age of seven. It's just the belief you can do it.
"Hopefully it's the first of many for me. I just need to keep working hard and moving forward."
