Karan took to Twitter on Friday to laud Hrithik's performance.
"As a filmmaker it's exhilarating to watch an actor deliver his best....Hrithik is a power house talent and is exemplary in 'Kaabil'," Karan tweeted.
Karan and Hrithik have worked together in 2001 film "Kabhi Khushi Kabhie Gham..."
"Kaabil" is a love story of a blind couple. The film shows what sets the man on a revenge spree against the villains essayed by Rohit and Ronit Roy.
The film also features actress Yami Gautam, who has shared screen space with the "Bang Bang!" star for the first time.