Bonucci spent a single season with the Rossoneri, returning to the Serie A champions with Mattia Caldara and Gonzalo Higuain both moving to San Siro.
Italy centre-back Bonucci captained Milan during his year at the club and Suso feels the 31-year-old will be missed, although he is happy to see Higuain arrive.
"Yes, we lose leadership and experience," Suso told Marca of Bonucci's departure.
"He brought many things in a very young team. He feels he took a step back signing for Milan and that is why he returns to Juventus.
"When the project is interesting and players like Higuain arrive it is always positive. The level of the team increases.
"If the year is good for him, it will automatically be good for us too. He is a player who stands out well and knows what to do with the ball."
"We had several offers, four or five. But the club was not willing to negotiate," Suso added.
"I always say that I love Milan and my family is very happy. With the new owners we will sit down to talk to renew again. I renewed in November and may be able to do it again soon. And for me it is a pride.
"Although Juventus is now in charge of the titles, one knows and feels that Milan is one of the strongest clubs. It will be a joy to say that I have been an important player in Milan."