Both players arrived in the summer, with Real Madrid legend Modric making a major impact on the title contenders.
Rabiot told La Gazzetta dello Sport: "He's a simple person and loves football like a child.
"I've felt very comfortable with him in midfield since day one because he has quality, vision, and makes a huge contribution even when winning the ball back, running and cutting in decisively when needed.
"He's an extraordinary player who amazes me with the desire he shows on the pitch every day, even at 40."
Rabiot also said of teammate Rafael Leao, adding: "He puts a lot of effort into training, and today for example, he made some defensive slides to win the ball back: it's nice to see a talent like Rafa sacrificing himself for the team.
"Compared to when I was at Juve, he's improved a lot."