The 34-year old could quite possibly be in his final campaign as he continues to juggle international games with Wales and club obligations with Cardiff while battling ongoing knee problems.
"Craig is quite open in talking about it (retirement) so it's not a shock to anyone if it happens at the end of the season," said Mackay.
"He's someone at ease with seeing how the season goes and making that decision in the summer.
"I talk to him about Kevin Phillips and Ryan Giggs, who take it a season at a time, but there will be a point where, because of his knees, Craig wants a life with his family where he can walk about and not have arthritis in his knees for the rest of his life.
"And there'll be a point where he says 'that's not quite yet, I'm going to have another season'.
"There might be a point where he finally decides 'I've sweated and given blood for my country for a long time and I'll now come out of that to elongate my career'.
"But that will be something he'll decide. I'm quite relaxed.