Andrea Pirlo felt Juventus' youngsters proved they were "up to it" but said they must be more ruthless after needing extra time to beat Genoa 3-2 in the Coppa Italia.
Juve dominated Serie A strugglers Genoa in the first half at Allianz Stadium on Wednesday, the lively Dejan Kulusevski opening the scoring inside two minutes before laying on a second goal for Alvaro Morata.
Lennart Czyborra halved the deficit with a header against the run of play midway through the first half and Filippo Melegoni forced extra time with a great finish from 25 yards out.
Cristiano Ronaldo was introduced as a substitute late in normal time, but it was 21-year-old debutant Hamza Rafia who settled it late in the first period of extra time.
Radu Dragusin and Manolo Portanova were among the other young players given an opportunity by Pirlo on a night which saw a much-changed Juve side have 24 shots, 13 of which were on target, as they made hard work of setting up a quarter-final tie against Sassuolo or SPAL.
Pirlo was impressed by the Juve youngsters, but was frustrated the Serie A champions were taken to extra time ahead of a clash with Inter on Sunday.
He said: "They played a great match, I'm happy for them because they proved to be up to it. Too bad the game was complicated, we had to close it in the first half."
Pirlo added: "It happens that every now and then when we think the race is over we lose focus, thinking it's all easy, but if you don't have your head right they become complicated games.
"As happened today when we went to extra time, we lost energy and had to finish it in the first half."
Kulusevski staked his claim for a regular starting berth, hitting the target with four of his five shots and making four key passes as he tormented Genoa in a classy performance.
Pirlo was not surprised to see the Sweden midfielder and striker Morata, starting for the first time since recovering from a thigh injury, link up so effectively.
The former Italy playmaker said: "They had a great understanding, especially in the first half when they played very close and played for each other.
"They have been training together since the beginning of the season and they know what their characteristics are and how to look for each other and tonight they proved it."