The Bluebirds' manager's remarks came after he witnessed his side secure a 3-2 win over Manchester City yesterday.
When asked by talkSPORT if he wants to bring in some new faces, Mackay said: "Yeah. I'm trying to add quality rather than quantity because they have got to be better or the same as the type of guy that I have got in at the club. We are trying hard, but it's not easy."
The former Championship outfit have spent £25m so far in the window.