Mauri signed for the Rossoneri yesterday on a free transfer.
"I'm happy, not just for me, but especially for the lad," agent Dino Zappacosta told the Gianluca di Marzio website.
“He's going to play for one of the most successful clubs in the world, and one of the biggest. Sure, they've had problems in the past two years, but I have no doubt they can get back to where they belong.
“Football goes in cycles. I hope the lad can play his part, the potential is all there. He can show he's a great player.
“The negotiations haven't been fast, there were a lot of teams after the player. He's proven to be very good, he's 19 and has played a lot of games [already].
“When I told him all the options, he always indicated that Milan would be a welcome club. He told me that he won't go to make up the numbers, he's going there to play.
“[Milan CEO Adriano] Galliani already wanted him in January, now hopefully he [Mauri] can repay him. In recent days, other clubs showed interest, but Milan didn't hesitate to close the deal."