Defender CJ Egan-Riley played the full 90 minutes at the Etihad Stadium, as City advanced through to the quarter-finals with a 5-0 aggregate victory.
Attacking midfielder James McAtee was a half-time substitute for fellow academy graduate Phil Foden, while Pep Guardiola also handed a European bow to defender Luke Mbete against the Portuguese side.
And Gundogan attributed our of our youngsters' successful progression to the efforts he has witnessed first hand on the training pitch.
He said: "We were able to put out a few young lads today, (it was) great to see them do the work and get rewarded for the work.
"Macca (James McAtee) has already been training for a long time with us, he got a couple of games so you could see already in training all these abilities and potentials.
"CJ, it was his (Champions League) debut tonight and what a debut.
"I’m really happy for the boy, I think he played in a really mature way, avoided simple mistakes and even though he was maybe a little bit nervous and excited, I think he was able to control his emotions very well.
"It shows that hard work always pays off and they deserved it today."
Watch Ilkay's post-match interview in full via the video at the top of this page.