Federici was Royals' man of the match as they were knocked out of the FA Cup at Old Trafford on Monday night.
Karacan told the Reading Post: "He got a lot of unfair stick at the start of the season, but he has been unbelievable for us ever since he came to the club.
"He showed against Man United how good he is in this league and in this country. He doesn't need a pat on the back from us. He knows how he helped keep us in the game at Old Trafford.
"Feds deserves all the credit he gets. He is a future Australia No. 1 and I'm sure he will go on to better things."