Trailing 2-0 from the home leg - in which Alex Telles was sent off midway through the first half - Porto were beaten 1-0 at Juventus Stadium thanks to Paulo Dybala's penalty.
The spot-kick was awarded after Maxi Pereira was sent off for handball on the line, leaving Porto with an almost impossible task to advance to the quarter-finals.
That proved well beyond them, but Nuno was nonetheless proud of the way his players and supporters represented the club in another difficult outing.
"The red card was decisive, as it had been in the first leg," he said. "There will always be a doubt about what we could have achieved with 11 players for the entire time in both games.
"Tonight we simply wanted to be ourselves and play our game, the same way we always do. We started well, we had possession, we showed quality, we defended well and we were solid.
"We knew we had to score at least two goals, but we didn't want to lose our identity. And we didn't until the red card.
"In the second half I have to salute the support we had from our fans. It was their support that gave us the strength to keep our balance, to not concede any more goals and to even create a few chances in the second 45 minutes.
"We leave more united than ever."