The 21-year-old forward has failed to find the net for the Giallorossi since his big-money move from Siena in the summer.
"I do not understand the criticism," he told gazzettagiallorossa.it. "A player cannot be judged only on his goals, but on how he plays. I was at the game [against Atalanta] on Sunday. I saw Mattia play a great match, and this was also emphasised by [Roma Coach] Zdenek Zeman.
"Unfortunately for attackers, it is always the same. It is fans' culture that is wrong. We should look at the whole game, not just the one shot that may go in.
"Everything is good with Zeman. Mattia has had a difficult summer where he joined the group a month later than everyone else. We should talk again in a month's time when he is 100 per cent.
"Mattia was aware [when he joined Roma] that there is great competition [for places]. That happens everywhere - at Milan, Inter, Juventus and Lazio. When you play at a top club, you have to be aware that there is going to be someone else who wants your place in the team."