The 52-year-old believes the former Barcelona youngster has what it takes to become a great striker with the right attitude
The Argentine youngster netted twice against his former team to take his tally for 2013-14 to eight goals in 18 league appearances.
Mazzarri has little doubt that the striker can become a great player if he focuses on his performances on the pitch, although the Inter boss was not impressed with Icardi's inflammatory celebration after his first strike.
"He showed great personality in a hostile environment. I don't think he should have made that gesture, but he did his thing," he said at a press conference.
"If he can keep this up and get some flaws out of his game, he can become a true great. He has all the characteristics of a real striker.
"He has to focus on his game and I have told him just that. He should not let personal affairs affect his form on the pitch."
Inter sit fifth in the Serie A table following this week's results with 53 points from 33 games.