City's summer signing scored with a thumping header from Kevin McNaughton's cross to set City on their way to a 4 - 3 win at Forest Green last night.
"I thought he did fantastically well, he's got a good touch and he's an international footballer," said Mackay.
"I thought he had some good movement, good touches and he took his goal very well obviously."
Cardiff's other goals came from Nicky Maynard, Peter Whittingham and Craig Noone.
Source: Cardiff City Online