Bennett had been holding contract talks with club bosses before and after serious injury struck in March. No deal has been reached, and the man described by chairman Mehmet Dalman as "the best left back in the league" leaves for nothing at the end of his current contract.
Not sure what the extent of the serious injury is (aged 31) but obviously if he can recover we need a reliable left back.
Edit:
Cardiff say scans show Bennett, 30, suffered an anterior cruciate ligament injury and that he will now see a specialist.
"When someone goes down like that and doesn't move, you know they are hurt," McCarthy told BBC Sport Wales after the Derby game.
"He's not good. I'm not a doctor or a surgeon but he'll be assessed tomorrow. He's not in good shape anyway."
Bit of a risk, reading that.