The 23-year old South Korean winger was used as a substitute for the sixth time this campaign, to make it 13 appearances total for the Bluebirds, and netted his first goal in the 85th minute to round out the victory which sent the Welsh club three points clear on top of the Championship table.
Mackay was full of praise for both Kim, and Joe Mason, after they scored off the bench and feels his squad is in much better shape this season than last.
"Both Joe and Bo-Kyung are players I know can come on and make an impact, which from the bench is probably the difference between this year and last year when we had youngsters coming on as substitutes," Malky stold the club's official website.
"This year we have people coming on who can make a real impact. Craig (Bellamy) with his fantastic running beyond and the problems he was causing, scoring a fantastic second goal for us and running himself into the ground.
"Then it was time to get some fresh legs on there with Joe - and I felt the same in midfield in terms of taking Craig Noone off. He put a fantastic ball in for the first goal and caused problems throughout, but it was time to take him off and put Kim on, who keeps the ball very well.
"The whole move between his breaking play up, linking with Heidar who's run was superb, giving it back to Kim to then score a beautiful goal."