Mackay said he was still working hard to recruit another player.
"We're trying hard and we're going to make sure we do everything we can right up to Monday," Mackay told BBC Sport.
"We would like to at least get one more in, but it's not easy because they have to be players that bring more quality, rather than the quantity of bringing three or four people in in the last week and just filling up a squad.
"I've got good players here, I've got very good players here, whoever comes in has to add to that.
"That being the case, we are still trying. We are under competition from other (clubs) because that's what good players bring.
"But we're trying hard and we're going to make sure we do everything we can right up to Monday."
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