The former Real Madrid star failed to score on the day.
But Allegri said, “Ronaldo held out well physically, has only been training with us for seven days and did really well. It's a pity he wasn't able to score a goal.
“It depends on the characteristics of the players near him. Ronaldo had several shots on target today, Sorrentino made several saves, there were also some good movements that were not rewarded by the midfielders. Those are movements that must be read from the back with the ball provided in the right spot.
“I was most impressed that Ronaldo settled in to the team, he was very happy in the locker room and had his chances.
“The main problem tonight was we let the concentration levels drop and we simply cannot afford to do that."