"The experiment didn't go very well. We had practically no pressing with the forwards in the first half, which created huge gaps and created big problems," Mancini told to RAI Sport.
"The second half was good. In the first, we wasted a chance straight away, then we made a lot of technical errors under their press to go on the counter-attack. We suffered more there,
"I thought we did better after the break and were only missing a goal. Some of these players hadn't been on the field for a while and it will take some time."
European champions Italy will take a break until the new year. Their next scheduled match is a European Championship qualifier against England in March.
"I saw a good side in the second half and we were just unlucky not to score, but they had the chances," Mancini said.
"It's a pity that we end the year with defeat."