Late goals from Jose Gimenez and Diego Godin, gave Atletico a deserved win in the first leg of the Champions League last-16 tie at the Wanda Metropolitano.
Ronaldo had just one shot on target and Godin’s goal deflected in off him in the 83rd minute.
But Allegri backed the 34-year-old’s performance and said the clash would be beneficial heading into the second leg in Turin on March 12.
“Ronaldo played a good game.
“He is confident with these kinds of matches. He was not bad at all.
“We missed all the second half as a team. And this match will be useful looking forward to the second leg,” Allegri told a news conference.