The 23-year old joined the Bluebirds from Japanese side Cerezo Osaka last summer before going on to make 28 appearances in their title-winning campaign.
Kim could become only the 12th South Korean player to feature in England's top-flight, but Mackay believes he will have no problems finding his feet.
"I think Kim is absolutely ready to make the step up to the Premier League," he told Wales Online.
"He's an international, very comfortable on the ball and just desperate not to give it away. He is certainly a very exciting player, and that was the reason I bought him in the first place.
"I think it was a case of us getting a player that ordinarily we might not have managed to get."