Nainggolan felt they failed to do the "dirty work" to match Juve on the night.
“We prepared a different match, but we had chances," Nainggolan lamented, speaking to Roma TV.
“We could have had at least a couple of goals, but if you don't make the most of your chances it's tough to beat certain teams and it's hard here.
“We improved compared to last year in some respects, even though we were scoring goals more easily.
“They scored because of our carelessness, and in my opinion incidents decided the game.
“If you look at Juve's goal you can see how ruthless they are, we have to do the dirty work and be more decisive ourselves, there was always something missing even if we had chances."