Cardiff City host Manchester United on Sunday, and the boss of the Welsh side has no doubt the 'iconic' midfielder will make the step up to management in the future
Giggs has played and scored in all previous 21 Premier League seasons, but faces his hometown club for the first time on Sunday.
And Mackay was quick to laud the decorated 40-year-old, who is now a player-coach at Old Trafford.
"Every day of the week, every week of the year for the last 15 years he has been a top player," Mackay told reporters.
"He is a top bloke and he is probably my favourite player of the last 15 years."
Mackay also expects Giggs to make the move into management when he finally brings an end to his illustrious playing career.
Mackay added: "I met him a couple of weeks ago at the FA Pro Licence course I was talking at.
"He is now stepping into the other side of the game in that player-coach role I had at one point and a lot of players have had at some point when their careers are finishing."
He continued: "He is obviously an iconic figure here [in Cardiff] for what he has done for Wales and I have no doubt at one point he will end up in management.
"He has learned from the best [in Sir Alex Ferguson] and it will be good to see him on Sunday."