Mackay said: "This was a really big win for us after losing to Peterborough and it was smashing the way we bounced back from that. I'm delighted.
"We knew we were coming to play a very good team and that it was going to be tough.
"But I think this was a great advert for the Championship - and I'm not saying that just because we won. It was two teams playing attractive football and at a hell of a tempo.
"The goal was a great strike from (Craig) Bellamy and it showed the quality we have.
"But it was just as impressive to see the way he was closing players down in the last five minutes of the game. It shows what a team player he is.
"He is beginning to get match-fit, because he has been unfortunate with injuries.
"In this game he never gave the defenders a minute's peace. He is comfortable being with this group of players and enjoying his football.
"But it was also a good defensive performance all round, and I think David Marshall is the best goalkeeper in the division."