The Brazilian winger has joined the Azzurri on-loan from Sporting CP to the end of the season with an option to buy.
Silas coached Alisson at Unaio Leiria and was asked if he could be compared with AC Milan star Rafael Leao.
He told TMW: "I think he's a bit different from Rafa, even if they have some similarities. If Leao finds space on the wing or behind the defense, he can be very dangerous.
"Alisson too, but I think he can be even more dangerous closer to the penalty area, even with less space available. In this respect, he might already be more dangerous than Leao, with his very powerful shot and dribbling ability.
"Rafa is also physically bigger, so I don't see many similarities between the two."
On his best qualities, Silas also said: "Dribbling and shooting. Whenever he gets the ball in the final third of the pitch, especially as a left winger, he's focused on goal and shooting. He's good with both his right and left foot.
"And he can provide assists."
"I think people will have to be patient for a short period, after which he can make a difference, even with 10 minutes at his disposal."