The Paraguay international boasts a remarkable scoring record in the Portuguese top flight and has been linked with a move to pastures new for some time.
Manchester City were reported to be leading the chase for his signature this summer, with new Blues boss Manuel Pellegrini in the hunt for attacking talent after losing Carlos Tevez to Juventus.
Man City have yet to put a deal in place, though, meaning other clubs are free to join the chase.
Cardiff could be about to test the water with an official approach, as they continue with their efforts to piece together a squad that can compete at a Premier League level.
Mackay is actively scouring the market for suitable recruits and has conceded that Cardozo - a man who netted 33 times in 46 appearances last season - would be of interest to him.
He told Portuguese newspaper Record: "I know all about the attributes of Cardozo. I know exactly how he plays.
"I think he would suit our game and would be interesting for us."