Brescia midfielder Tonali was called up after impressing in Serie B this season, building on his two goals in 19 appearances in 2017-18 with another strike in his first 11 games this term.
The 18-year-old, who has been likened to Andrea Pirlo, has attracted the interest of several top clubs including Chelsea, Juventus and Napoli, Goal understands.
And Mancini heaped praise on Tonali as he looked forward to the opportunity to add to his side's 1-0 Nations League victory over Poland in October - their first win in six matches.
When asked about Tonali, Mancini told reporters: "I want to stress again that he's incredibly gifted and has clear margins for growth.
"I'll get to know him better over the next few days."
Victory over Poland kept Italy's hopes of a place in the Nations League final four alive and Mancini called for a repeat performance against League A Group 3 leaders Portugal.
"We want to continue along the same path from the Poland game," said Mancini. "We can improve on many things, especially by being more clinical in front of goal.
"We're fighting for first place. Winning must always be our objective.
"No one is excluded, let's make that clear. There is still time to build a group. Whoever proves themselves can play a part.
"We must play good football and look to win the fans back. We are Italy."