The 25-year-old midfielder re-joined the Blues from Benfica nearly two weeks ago after initially leaving Stamford Bridge in 2011.
Ivanovic believes that his fellow Serbian has improved since returning to the club and can make a big impact in the years to come.
"He's the one who's leading the game, he asks for the ball, goes forward and defensively he's improved a lot," Ivanovic told Chelsea's official website.
"He can be very important for us, he's signed for five years so his future is here and step by step he will become one of the most important players.
"He's now a proper player, he's come back after three years in Portugal where the people loved him there and he played very well, so he has more confidence and a different attitude."
Chelsea are believed to have paid Benfica around £21m for the return of Matic.