Mancini was booed when he chose to take off the Argie hitman, rather than the out-of-sorts Edin Dzeko.
But the Italian defended his decision, saying: "I have my reasons for doing this - I am not stupid.
"I understand the supporters reaction.
"But Everton can score from set-pieces and I needed a tall player to help the defenders.
"I also felt that Dzeko could score a goal."