Mignolet has been criticised for his performances this season by legendary Anfield keeper Bruce Grobbelaar.
Rodgers told the Liverpool Echo: "He has come into a huge club and replaced a legendary figure at the club in Pepe Reina.
"That was always going to take a bit of time.
"But over the course of the season he has made a big contribution. I don’t forget the significance of some of the saves he has made.
"Simon hasn’t ever cost us a game but he has certainly gained us points. He’s an excellent goalkeeper."