Whittingham converted superbly at the far post from Craig Noone's cross in the 65th minute to give Cardiff a deserved three points which gave them some valuable breathing space over the bottom three.
"I'm delighted for him because he's been one of my most consistent performers this year," said Mackay.
"He had a period out of the side near the end of last season but really came back in the summer with a renewed belief in his own ability.
"He worked hard on his body to survive in the Premier League in midfield and he's showing that this season."
The method of Whittingham's goal may have been unfamiliar but Mackay revealed he had been on the receiving end the last time the playmaker scored with his head.
"Peter scored a headed goal against me when I was the manager of Watford about four years ago," he said.
"I told him that. I said, 'do you remember the last time you scored a header?' and he went, 'against you at Watford'."
For breaking stories and all the great banter like us on Facebook: facebook.com/tribalfootball