Bellamy spent last season on loan at Cardiff from Manchester City and scored 11 goals as the Welsh side missed out on promotion from the Championship.
The 31-year-old is still under contract back at Eastlands and has been linked with a return to the Cardiff City Stadium and Mackay is not ruling out an attempt to re-sign the Wales international.
"Craig is a player I have kept in touch with as we played together at Norwich, so he is someone I know very well," said Mackay.
"He did well for this football club last year and we all know he is someone affected by Cardiff City - he is a local boy.
"He is someone who, in this division, is an X-factor player.
"But Craig is contracted to Manchester City so it would be wrong of me to talk too much about him."
Bluebirds chief executive Gethin Jenkins added: "When the time is right - Craig is away at the minute - then we will sit down like we did last year and have the appropriate conversation with Craig and City."