Stephan El Shaarawy fired home just after half time, but the 45-year-old tactician has conceded that there was an offside.
"The first goal from El Shaarawy was offside," he told Sky Sport Italia. "It was easy to see. It was tough on Catania, because they played a really good game.
"The first half was very even, but we improved vastly in the second half.
"It is an important win for us and it allows us to continue the good form we are on."