The 19-year-old, who proved crucial in helping Pescara gain promotion to Serie A this season, is set to join Paris Saint-Germain on a permanent transfer later this week.
The Ligue 1 giants are set to pay 14 million euros to Pescara to sign the Italy U21 player.
"Italian clubs don't think they can spend money on Italian players," Sebastiani said to Italian radio station Radio Mana Sport. "Should Verratti go abroad, it will be a defeat for our football.
"Clubs do spend money on young foreign players because they are considered much stronger than Italian players.
"For Verratti, to join Paris Saint-Germain is a great opportunity."
Verratti has made 74 appearances for Pescara since making his debut with the Italian outfit at the age of 16.
He is set to sign a five-year deal with the Parisien giants.