Milinkovic-Savic, 23, has been strongly linked with the likes of Real Madrid and Manchester United in recent weeks.
According to former Chelsea striker Kezman, his client is already better than United midfielder Paul Pogba, and will ultimately become "a candidate for the Ballon d'Or" due to his incredible ability.
"When Sergej came to Italy, he was compared with Pogba, because at that moment it was probably the easiest comparison to make in terms of characteristics," Kezman told Mozzart Sport.
"I do really respect Pogba, let's be clear, and other linkers who can run and work for the team, but I think now Sergej has different and better quality than Pogba. Over the last six months, he has made enormous progress at Lazio. If he retains his health, he can become the most complete player on the planet.
"He has remarkable attributes and you'll not find another player in the world with that power, muscular structure and height combined with technique and tactical awareness. He has the touch of a Brazilian and some of the things he does remind me of Zinedine Zidane.
"Milinkovic-Savic is the most effective midfielder in Europe right now, as he can score goals in a variety of ways and has a good head on his shoulders. I've played with Arjen Robben, Frank Lampard and some of the best in Europe and I think Sergej can surpass them if he keeps this up. He could soon be a candidate for the Ballon d'Or."
Milinkovic-Savic, who has also been linked with Paris Saint-Germain and Juventus, has scored 11 times and registered six assists in 34 appearances for Lazio this season.